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Profile of a psychologist: Philip Zimbardo

Philip Zimbardo, Psychology

Philip Zimbardo, Psychology

Philip G. Zimbardo is world renowned for his controversial study, the Stanford Prison experiment. In more recent years he has become known for his theory known as the “Lucifer Effect,” in which he investigates the question “What makes good people do bad things?” A Professor Emeritus of Psychology at Stanford University and currently still teaching, Zimbardo also holds the title of two-time past president of the Western Psychological Association and past president of the American Psychological Association. As a social psychologist, Zimbardo constantly questions how we interact and influence others in our society; however, most notably, he seeks to discover how our environment is and will remain our strongest influence.

Philip Zimbardo was born in 1933 to a Sicilian-American family in New York City, New York. His academic career landed him classmates with another future social psychologist, Stanley Milgram, in James Monroe High School. Next he merited a BA from Brooklyn College and a PhD from Yale University. After several years of teaching a universities all across the United States, he finally started his professorship at Stanford in 1968. Since 2000, Zimbardo has been on a mission to bring psychology to the forefront of research and also the public eye by presenting a TV series on “discovering psychology” and lecturing at TED, to name a few.

zimbardo2Inspired by Stanley Milgram’s obedience studies in 1963 that demonstrated the moral aberration people are willing to commit to obey authority, Zimbardo aimed to discover what makes people concede their moral compass when put in a place of power. Zimbardo wanted to uncover under what circumstances people would “willing use (or abuse) power granted to them.” In light of this curiosity, he carried out the Stanford Prison experiment in 1971. His subjects were twenty-four, mentally healthy, American, university students. The similarity of subjects attempted to control for all dependent variables. Randomly, the students were assigned the role of “guard or prisoner.” Then one morning the “prisoners” were arrested by real police officers whom booked to them be transferred to the mock prison built in the basement of the Stanford Psychology Department.

zimbardo3Once transferred into the “prison,” the “prisoners” were “stripped, searched, deloused, and given uniforms and bedding.” The prisoners were then stripped of their identify and dehumanised by the “guards” who were told to  refer to them by assigned numbers. To heighten their lack of freedom, the “prisoners” also had a chain bolted around one ankle. The “guards” wore military inspired uniforms, sunglasses (to prevent eye-contact) in addition to carrying keys, whistles, handcuffs and clubs. The “guards” patrolled 24 hours a day and where given full control of the “prisoners” to maintain order. It did not take long for the environment to quickly turn “threatening” forcing the experiment to end prematurely after only six days.

Every single “guard” became “abusive and authoritarian; prisoners were denied food or bedding, hooded, chained, and made to clean toilet bowls with their hands.” The “prisoners” were used as playthings to take part in the “guards” degrading games. One prisoner had to be released after only thirty-six hours after suffering a nervous break.

Zimbardo’s findings, the basis for the Lucifer Effect showed the world that good people can be induced to evil by “immersion” in “total situations.” Total situations have an “apparently legitimizing ideology and approved rules and roles.”  Zimbardo served as an expert witness in the defense of a guard during the Abu Ghraib trails, which as Zimbardo discusses in his TED video, showed many parallels with the Stanford Prison Experiment. The Abu Ghraib prison abuse against Iraqi prisoners by American soliders gathered wide controversy. Please view the TED video for further information. The scary thing Zimbardo explains is that “any deed that any human being has even done, however horrible, is possible for any of us to do – under the right or wrong situational pressures.” However, as Zimbardo discusses in his final chapter of The Lucifier Effect, his book, these situational pressures not only shows human capacity for evil but also for heroism.

Citations:

Collin, Catherine. The Psychology Book. New York: DK Pub., 2012. Print.

“Philip G. Zimbardo.” Philip G. Zimbardo. N.p., n.d. Web. 09 Aug. 2012. <http://www.zimbardo.com/&gt;.

Zimbardo, Philip G. The Lucifer Effect: Understanding How Good People Turn Evil. New York: Random House, 2007. Print.

Profile of a Psychologis: Hermann Ebbinghaus

herrmannBorn in Bramen, Germany in 1850, Ebbinghaus was the first psychologist to study learning and memory by conducting experiments on himself. At age seventeen, he commenced his study of philosophy at Bonn University on the eve of the Franco-Prussian War. After completing his studies, he travelled to France and England, conducting research on the “power of memory.” In 1885, he published Memory “detailing the nonsense syllable” research. The nonsense syllable, logatome or pseudoword is a string of syllables that resembles a real word is in fact “nonsense.” In the psychology of learning nonsense syllables are used as a way to examine speech recognition. After becoming professor at Berlin University, he established two psychological laboratories there. Finally, he moved to Berslau University, founded another laboratory, teaching there until his death in 1909.

Inspired by philosophers by the likes of John Locke and David Hume, Ebbinghaus argued that “remembering involves association,” linking things or ideas by similarities such as “time, place, cause or effect.” The goal of his research was to test how association can improve memory. To verify the accuracy of his findings, he recorded the results mathematically to see if “memory follows verifiable patterns.” This would become known as the Forgetting Curve.

To start his memory experiments, Ebbinghaus began by memorising lists of words to test his recall abilities. He then created 2,3000 nonsense syllables, three letters each with the same pattern consonant-vowel-consonant, to prevent association. He then grouped these nonsense syllables into lists, looked over the list for a few seconds, waited fifteen seconds to then try a second time. He then repeated his process until he could correctly recite the series. Alternating the list lengths and learning intervals, Ebbinghaus also tested how these variables effected the speed of learning and forgetting.

herrmann1Ebbinghaus discovered that material  he found meaningful, such as a poem, was up to ten times more easily remembered than the nonsense syllables. He also found that more time he spent memorising the list, the easier it was and the less time it took to reproduce the list from memory. In addition, he found that the information remembered after the first repetitions, were the most effectively remembered after time had passed. Finally, Ebbinghaus also found that typically, a very rapid loss of recall occurs in the first hour, followed by lowered rate of recall loss. To clarify, after nine hours sixty percent is forgotten and after twenty four hours, two-thirds of recall is lost. Plotted on a mathematical graph, Ebbinghaus’s findings shows a clear “forgetting curve” starting with a “sharp drop, followed by a shallow slope.”

Ebbinghaus’ findings still remain the basis of the psychology of learning and memory.

Citation:

Collin, Catherine. The Psychology Book. New York: DK Pub., 2012. Print.

The Brain: Introduction, Brain Scans and Imagery

Scanning of a human brain by X-rays

Scanning of a human brain by X-rays

The brain enables the mind: seeing, hearing, remembering, thinking, feeling, speaking and dreaming.

Science now enables us to know about the living brain through lesions. Lesions are destroyed tissue. A brain lesion is naturally or experimentally caused destruction of brain tissue, which selectively removes tiny clusters of normal or defective brain cells without harming the surroundings. We can also probe the brain with tiny electrical pulses. Scientists can look upon on the messages of individual neurons and on mass action of billions of neurons. We can see colour representations of the brain’s energy – their consuming activity. These tools facilitated the neuroscience revolution.

The oldest method of studying the brain-mind connection is to observe the effects of brain disease and injuries. This has been going on for more than five thousand years. In the past two centuries, physicians have been recording the results of damage to specific brain areas. Some noticed that damage to one side of the brain often caused numbness or paralysis on the opposite side of body. This suggested that that somehow the right side of the body is wires to the left side and vice versa.

Other scientists noticed that damage of the back of brain disrupted vision and that damage to the left front part of the brain caused speech difficulties. These discoveries have helped scientists map the brain. Today scientists are able to electrically, chemically or magnetically stimulate various parts of the brain to record the effects. Modern electrodes are so small that they can detect the electro pulse in a single neuron.

scan2An electroencephalogram or EEG is an amplified recording of the waves of electrical activity that travels across the brain’s surface. These waves are measured by electrodes placed on the scalp when presented with a stimulus.

A positron emission tomography or PET scan is a visual display of brain activity. It detects where a radioactive form of glucose travels to whists the brain performs a given task.

A magnetic resonance imaging system or an MRI is a technique that uses magnetic fields and radio waves to produce computer generated images that distinguish among different types of soft tissue. It also allows us to see structures within in the brain. MRIs align the spinning atoms in our brain through the use of a magnetic field as well as causing a pulse of radio waves that disorients them momentarily. When the atoms return to normal spin the release detectable signals. MRIs can also detect oxygen-laden blood flow.

Citation

Myers, David G. Psychology . 6. Worth Publishers, 2001. Print.Myers, David G. Psychology . 6. Worth Publishers,2001. Print.

Profile of a Psychologist: Paul Ekman

ekmanSome of you may have seen the crime-procedural drama “Lie to Me.” It ran on FOX between 2009-2011 until it got cancelled. The show stared  Tim Roth as Cal Lightman, who along with his colleagues of the Lightman Group were consultants for the police and FBI. The Lightman Group specialised in applied psychology, specifically interpreting mirco-expressions and body language. What many people may not know; however, is that the techniques utilised by the Lightman Group in “Lie to Me” are based on the work of psychologist Paul Ekman.

Ekman was born in Newark, New Jersey in 1934 but after the outbreak of World War II, moved across the country. At a mere fifteen, Ekman joined the University of Chicago where he became interested in “Freud and psychotherapy.” This inspired him to apply to Adelphi University where he earned his doctorate in clinical psychology. After a stunt working for the US Army, he went on to join the University of San Francisco where he began research into “nonverbal behaviour and facial expressions.” This work lead to further studies on the “concealment of emotions in facial expressions.” Being appointed to professor of psychology at UCSF in 1972, Ekman stayed there until his retirement in 2004.

Emotions play a huge role in emotional disorders and psychotherapy; however, when Ekman began his studies in the 70s, the subfield was practically unexplored. In the early days of psychotherapy emotions were seen as symptoms rather than “something to examined in their own right.” Ekman was one the first psychologists to realise that emotions are as much a vital part in psychotherapy as processes, drives and behaviour. He came to realise the importance of emotions through his work with nonverbal behaviour and facial expressions.

ekman2Before Ekman’s experiments it was believed that physical expression of emotions were learnt according to a set of social conventions, implying that how we express ourselves differes from culture to culture. However, through his travels across the globe, photographing people – ranging from developed countries to untouched tribes in the Amazon – he found that even the tribespeople, untouched by media and the outside world, could interpret emotions through facial expressions as well as people in developed countries. This suggests that physical expression of emotions are universal and a product of evolution not social conventions. A post in the Immersion Blog makes a great point regarding Ekman’s credibility, which has been disputed by critics claiming that facial expressions are for communications purposes only and not subconsciously reflecting our internal life. Robbie Cooper, the blogger, refutes this claim arguing that

                “We only think about expression when we want to use our body for communication on a conscious level. And a lot of the time we aren’t very good at faking internal states. If someone is playing a role in a social situation, it’s often expected of them, but much of the time we aren’t fooled by the performance. Which I think is one of the reasons why great actors are fascinating.” 

Ekman put forth six basic emotions – surprise, anger, happiness, fear, sadness and disgust – and decided because of their ubiquitous nature, these six basic emotions must be quintessential to our psychological make-up. He noted that specific facial expressions relate to each one of these six basic emotions and must in turn be involuntary emotional responses. Furthermore, these responses occur before the mind has time to register the cause and can thus be read to reveal our internal state. Ekman’s research became the basis of his F.A.C.E. training programme aimed to familiarise people, specifically officers of the law and security professionals dealing with deception on a daily basis, with “microexpressions.” Microexpression is term coined by Ekman as the involuntary emotional response, reflected in our facial expression before our brain has time to process the cause.

In Ekman’s 2003 book, Emotions Revealed, he states that emotions can be far more powerful than any of the drives listed by Freud such as sex, hunger and the will for life. These revelations are revolutionary as they completely altered the way in which emotions were seen to play a role in psychological disorders. For example, unhappiness can override the will to live and fear and shame, a biproduct of trauma, can override sexual drive.

ekman3ekman4

itations:

Cooper, Robbie. “Ekman Emotion Recognition Test.” Web log post. Immersion Blog. N.p., 29 June 2009. Web. 21 Aug. 2012. <http://blog.robbiecooper.org/2009/06/29/ekman-emotion-recognition-test/&gt;.

Myers, David G. Psychology . 6. Worth Publishers, 2001. Print.Myers, David G. Psychology . 6. Worth Publishers,2001. Print.

Profile of a Psychologist: Carl Jung

JungBorn in a small village in Switzerland in 1875, Carl Gustav Jung grew up in a rather eccentric family. He became an excellent linguist at an early age and in 1903 married Emma Rausenbach, an intelligent young woman from a wealthy Swiss-German family. Emma later became a prominent psychoanalyst herself known as Emma Jung. Although originally educated as a psychiatrist, Jung’s meeting with Sigmund Freud in 1907, pushed him towards psychoanalysis setting him on the path towards becoming Freud’s protege. However, the pair became estranged as their theories diverged causing a permanent rift. Following World War I, Jung travelled across the globe studying native people, taking part in “anthropological and archaeological expeditions.” In 1935, Jung became professor at the University of Zurich before deciding to concentrate strictly on research.

Jung2

Freud first introduced the idea that humans are guided by forces within ourselves, specifically our unconscious. He claimed that our experience of the world is directly affected by “primal drives contained in the unconscious.” Jung expanded on this basic philosophy inquiring into the basic elements that “make up the unconscious and its workings.” He was most intrigued by striking similarities between societies around the world despite completely differing cultures. In particular, the similarities found in myths and symbols ranging across cultures. Jung believed this could be explained by “something larger than the individual experience of man.”

Jung3

To Jung it appeared that the existing commonality between these myths and symbols proved the existence of a “collective memory” passed down by generations as part of our heredity. He believed that this collective memory was housed in a part of the psyche and contained ideas “held in a timeless structure.” Finally, he proposed a notion that a distinct part of the unconscious is completely void of individual experiences, coining the term “collective unconscious.” Together with the ego, our conscious mind; the personal unconscious, our individual suppressed memories, the collective unconscious forms the three components of the psyche. We then inherit these collective memories found in the collective unconscious, allowing them to emerge within our own psyche creating symbols known as archetypes. Differing cultures, allow for layers and variations of these archetypes to exist simultaneously and just like with the evolution of all species on this planet, the layers of these archetypes reveal traces of the entire human experience.

Jung4

Finally, our inherited archetypes, etched deep within our unconscious, serve as templates used by our psyche to “organise and understand our own experience.” Basically, archetypes serve as a guidebook programmed within our minds to help us make sense of the world as well as to survive it. Archetypes serve as the foundational structure on which our experience builds. They can be seen as emotions or behavioural patterns; regardless, they help us determine “a particular set of…expressions as a unified pattern that has meaning” seemingly instinctually.

Furthermore, Jung also is renowned in the world of psychology for his exploration of word association and his concepts of introversion and extroversion. His concepts inspired many well-known personality tests used today such as Myer-Briggs Type Indicator.

If you are interested in Jung you should consider checking out the movie A Dangerous Method. Also click here to see photos of my recent trip to the Jung Institute in Zurich.

 

Citation:

Collin, Catherine. The Psychology Book. New York: DK Pub., 2012. Print.

 

The Brain: The Cerebral Cortex

brain-lobes-diagram

The cerebral cortex is the intricate fabric of interconnected neural cells that covers the cerebral hemisphere. It serves as the ultimate control and information processing centre. Humans have larger cortexes which enables us to be more adaptable, which gives us the ability to learn and think beyond basic survival instincts.

The cerebral cortex is made up of a sheet of cells that is 1/8 of an inch think and contains approximately 30 billion nerve cells. Glial cells or glue cells as they are commonly called, hold the nervous system together. They are NOT neurons but their own category of cells. Glial cells serve to support, nourish and protect neurons by communicating with them. Scientists are currently attempting to find connection between glial cells and information transmission and memory.

brain lobes

Folds of the brain increase the brain’s surface area allowing for maximised function and activity. As most people know, the brain’s cerebral cortex consists of four lobes: the parietal lobe, the occipital lobe, the temporal lobe and the frontal lobe. The frontal lobe is the front portion of the cerebral cortex, lying right behind the forehead. The frontal lobe is involved in speaking, muscle movement, high level cognition (planning, judgment, reasoning). Damage to the frontal lobe can result in changes in social skills, libido, attention and risk-taking. The parietal lobe is the part of the cerebral cortex at the top of head, behind the frontal lobe towards the back. It includes the sensory cortex. This means the parietal lobe processes sensory information such as pain, touch and pressure. Damage to the parietal lobe results in sensory problems such as impaired verbal memory and language skills. The occipital lobe lies at the base of te head and includes the visual areas; it receives visual information from the opposite visual field. This means that what is seen by our right is processed by the left side of our occipital lobe and vice versa. The temporal lobe lies above the ears and includes the auditory areas. These two areas receive auditory information from the opposite ear much like how the eye and occipital lobe work. 

– Functions of the Cerebral Cortex –

German physicians Fritsch and Hitzig electrically stimulated the cerebral cortexes of dogs. Through their experiments, Fritsch and Hitzig found that they could make different parts of the dogs’ bodies move. However, their ability to make the dogs move through stimulation was selective. Movement was only observable when a specific arch-shaped area of the back of the frontal lobe was stimulated. This area is know known as the motor cortex. Furthermore, the physicians discovered that the parts of the body that were moved, corresponded to stimulation on the opposite side of the brain.

Neurosurgeons Foerster and Denfield also investigated the functions of the cerebral cortex through stimulation. They found that precise control requires the greatest amount of cortical space. Furthering this idea, Jose Delgado found that specific parts of the cerebral cortex correspond with certain actions. Today it is evident, through the use of MRI scans, that precise actions require overlapping cortical sites.

brain lobes 2

The cerebral cortex specialises in receiving information from the skin senses and the movement of body parts. The greater the area devoted to specific body region, the more sensitive this area becomes. As a paradigm, our lips are far smaller than our back; however, relative to size, the cerebral cortex dedicates far greater area to our lips making them far more sensitive and kisses so enjoyable. It also explains why our backs are far less sensitive to pain than say our stomachs.

– Association Functions – 

The association areas consist of 3/4 of the cerebral cortex. Association areas are uncommitted to sensory of muscular activity. They associate with various sensory inputs with stored memories. The functions of the association areas cannot be triggered by stimulation or any other forms of probing. The existence of these areas are vital in disproving the popular belief that 90% of our brain is dormant. Our brain relies heavily on these unassociated areas for interpretation, integration and acting on processed sensory information.

Citations:

Cherry, Kendra. “The Anatomy of the Brain.” The Four Lobes (2012): n. pag. About.com Psychology. Web. 03 Sept. 2012. <http://psychology.about.com/od/biopsychology/ss/brainstructure_2.htm&gt;.

Myers, David G. Psychology . 6. Worth Publishers, 2001. Print.Myers, David G. Psychology . 6. Worth Publishers,2001. Print.

The Brain: Plasticity

bp

Brain plasticity is the brain’s capacity for modification as evident in brain reorganization following immense learning, birth or damage. The younger we are, the greater our brain plasticity. As infants our brain’s capacity to change in response to stimuli is the greatest. This is due to the basic fact that as infants we have the immense responsibility to organise the world around us. Our neuroplasticity enables us to learn and begin to take in our surroundings. This plasticity is also seen in response to the learning and memorisation we experience through adulthood. Finally, however, brain plasticity is also seen following great brain damage. Plasticity enables our brains to compensate for lost function by emphasising remaining function. Infants and children have the greatest capacity to rebuild after brain damage as they still hold greater plasticity.

Master “stem cells” than can develop into any type of brain cells have been found in fetal brains. This discovery has raised hopes immensely of recovery mechanisms that would be able to mend damaged brains.

Spotlight Study: “Narcissistic Employee of the Month”

eotm

An assortment of studies from the United Kingdom have found a positive correlation between “pathological personality and success at work.” The studies, conducted on over 5,000 British workers have found that certain personality traits often consider dysfunctional, do in fact serve as an advantage in certain roles. A case study on author Joanne Limburg, a self-confessed perfectionist with OCD traits, encloses transparent sleeves with drafts of her poems to University of Cambridge. This obviously obsessive behaviour may seem completely unnecessary to most people; however, Limburg’s OCD tendencies to compulsively “triple-check and organise” makes people like her invaluable employees in “auditing and other detail-oriented work.”

Cognitive psychologist at New York University, Scott Barry Kaufman and researcher Adrian Furham have found that schizotypal people whom exhibit “some combination of social withdrawal, strange beliefs and cognitive disorganisation” display the extraordinary capacity to notice patterns others miss. Not to mention, people with this seemingly dysfunctional trait also show great promise in the arts as well as sales with their “out-of-the-box creativity.”

eotm2

Finally, professor Peter Harms of the University of Nebraska and Michael Maccoby of Oxford University have come to the conclusion that people with a “grandiose self-regarded” otherwise known as narcissism, can make excelled leaders. Narcissistic people believe that they are the personification of an excellent leader, pushing them to prove they are better than others meanwhile motivating others to learn and improve as well. Lastly, this grandiose self-regard leads narcissists to produce “beyond successful to world-changing” work.

Citation:

Yu, Alan. “ Narcissistic Employee of the Month. ” Psychology Today August 2012: 10. Print.

The Brain: Lateralisation of Brain Function

“The great pleasure and feeling in my right brain is more than my left brain can find the words to tell you.” – Roger Sperry

brain2

The left hemisphere of our brain functions in reading, writing, speaking, arithmetic, reasoning and understanding. It is considered the major hemisphere because it has proven far easier to comprehend and study. Our right brain to this day is still very much misunderstood.  We do know that the right hemisphere is immensely important to our creativity, expression and social skills such as recognising faces and tone of voice. However, diseases that afflict the right side of our brain still befuddle scientists today.

Popular psychology and self-help books discuss the left versus brain dominance. Creative, free-spirited people who have excellent social skills but are poor at maths are considered right brain dominant; whereas, logical, analytical, linear people lacking creativity are considered to be left brain dominant. Like most self-help fads, there is some truth behind these claims. Most people generally rely on one side of the brain more than the other whilst thinking. This is known as brain lateralisation, a term that grew out of work by American neurobiologist, Roger W. Sperry. That is to say that, people that rely more on their left brain whilst thinking do posses a more logical, linear, objective perspective than those who rely on their right brain more. However, it is important to understand that all humans rely on both hemispheres for day to day activities and hardly anyone displays solely the characteristics of one hemisphere.

brain3

The left and right hemispheres are connected by a large band of neural fibres called the corpus callosum. It allows for messages to be carried between the two hemispheres. Sperry along with other psychologists, Myers and Gazzinga, concluded through the splitting of the corpus callosum of animals left them relatively normal. These findings were then applied as a form of treatment for extreme cases of epilepsy – a neurological disorder marked by sensory disturbance, loss of consciousness and convulsions as a result of excessive nerve firing in the brain. In these extreme cases of epilepsy the excessive firing would start in one hemisphere but cascades into a storm of firing across the corpus callosum to the other hemisphere. A surgery in which the corpus callosum was split was seen as the only alternative to treat the worst symptoms. The surgery enabled the patients to carry out normal life without the constant life-threatening symptoms; however, through these experimental surgeries the function of the corpus callosum was discovered.

Sperry and Gazzangia found that the corpus callosum did, in fact, have significance.  It enables communication between the two hemispheres. Each hemisphere continues to learn after the operation; however, the two hemispheres remain unaware of any learning and experience of the other side.

Citations:

Cherry, Kendra. “The Anatomy of the Brain.” The Four Lobes (2012): n. pag.About.com Psychology. Web. 03 Sept. 2012. <http://psychology.about.com/od/biopsycholog

Myers, David G. Psychology . 6. Worth Publishers, 2001. Print.Myers, David G. Psychology . 6. Worth Publishers,2001. Print.

The Split Brain Experiments”. Nobelprize.org. 8 Sep 2012 http://www.nobelprize.org/educational/medicine/split-brain/background.html

 

Normal or Gaussian Distribution

Characteristics of Normal Distribution 

– Symmetrical about the mean

– Tails should meet the axis at infinity

– Bell-shaped distribution

– Mean = mode = median

– The area under the curve is 1 standard deviation away from the mean and makes up 68% of the entire distribution under the curve (This means that if you randomly select a point under the curve, there is a 68% chance it will fall one standard deviation from the mean)

– The area under the curve 1.96 SD (round to two) away from the mean makes up 95% of the entire distribution under the curve (This means that if you randomly select a point under the curve, there is a 95% chance it will fall 2 standard deviations from the mean)

– The sample mean = mean of the population

– The standard deviation of the mean distribution or standard error = (SD of the population)/(square root of the number of scores)

– The standard error indicates the degree to which sample means deviate from the mean

– The sample mean distribution converges to normal distribution as the size of the sample increases

– The bell-shaped curve can also be reflected in the lay-out of a histrogram

curve1

Here the SD is 15 units

curve2

Questions Dealing with Standard Deviation

Question: Assume the standard deviation is 10 and the mean score is 100. If you randomly select any point 1 standard deviation from the mean, what would be your range?

Answer: The range would be between 90 and 110. As one standard deviation is 10 units left or right. You could also say that you have a 68% chance of randomly picking a score between 90 and 110 on the this graph.

Question: Assume the standard deviation is 10 and the mean score is 100. If you randomly select any point 2 standard deviations from the mean, what would your range be?

Answer: The range would be between 80 and 120. As one standard deviation is 10 units left or right, 2 standard deviations would be 20 units left or right. You could also say that you have a 95% of randomly picking a score between 80 and 120 on this graph.

N.B: 95% is the commonly accepted probability, which is the alpha level or confidence level in psychological studies for rejecting the null hypothesis is p<0.05.

The z-Score 

It is possible to convert all normal distributions to the standard normal distribution.

For a standard normal distribution the mean has to equal 0 and the SD has to equal 1.

You can find the z-score by subtracting the mean from each data point, and then dividing the this zero-meaned data by the standard deviation.

If your final data point is +1, this point is one standard deviation above the mean. If your final data point is -3, this point is 3 standard deviations below the mean. The z-score is particularly useful for comparing data across different situations.

Error Bar Charts

Error bar charts are away of representing the confidence interval. Error bars display your mean means as a point on a chart and a vertical line through the mean point that represents the confidence interval. The longer the line, the longer the confidence interval. Error bar charts can also be used to see if two population means differ from each other by comparing confidence interval. If the confidence intervals do not overlap we can be 95% confident that both population means fall within the intervals indicated and therefore do not overlap.

curve3

Bibliography

ZHENG, Y. (2013). Referencing and citation – Harvard style, from PSY104 Methods and Reasoning for Psychologists. University of Sheffield, Richard Roberts Building on 11th February. Available from: Blackboard.
[Accessed 4/02/13].