# PSYC37H3 Lecture Notes - Lecture 4: Standard Deviation, Histogram, Psychological Testing

Psychological Assessment - Lecture #4; Jan 29/13

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Norms and Reliability

Big Five Personality Inventory

Based on one of the most well-validated and extensively studied models of normal

personality functioning

neuroticism - likelihood to experience negative emotions, high scores are worse to

have

extraversion - like social interactions, favour being social

openness to experience - trying new things, flexible to your ideas

agreeableness

conscientiousness - how diligent are you, are you going to get your work done on

time? are you going to meet deadlines

Scores range from 1(disagree strongly) to 5 (agree strongly)

Raw Scores

Raw scores in isolation are absolutely meaningless that compares to other tests where a

raw score can be meaningful

Become meaningful in relation (when you compare) to norms [compare score to a healthy

person/ average ]

Recall: Norm-referenced tests - the way we interpret scores is based on how the normal

person does, if it isn't a norm test then it would be a criterion test (when you meet all the

criteria)

Frequency Table

- contains raw scores for everyone in this class's responses to the neuroticism scale of the Big

Five Personality Inventory

How are these calculated?

by summing up each person's answers for the specific items on the inventory that make up

the neuroticism scale

Essential Statistical Concepts

Frequency Distributions

Histogram – method of summarizing data or test scores in graphic form [bar graph]

Frequency Polygon – similar to histogram except that the frequency of the class

intervals is represented by single points rather than columns [ line graph]

Psychological Assessment - Lecture #4; Jan 29/13

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Measures of Central Tendency

Mean – sum of all scores divided by number of scores [every score is taken into

consideration] - if there are extreme scores then it will affect the mean

Median – middlemost score when all scores have been ranked - better representation

sometimes of the mean

Mode – most frequently occurring score

Depending on the shape of the distribution these central tendencies can shift, if distribution

is perfectly symmetrical, all 3 are the same, when we're using a norm reference test we are

assuming the population is normally distributed

Measures of Variability

Standard deviation – conceptually, it is the degree of dispersion in a group of scores - need

an appropriate variability (not too much or not too little) to distinguish between people

Preferred measure of variability because of its direct relevance to the normal

distribution

Variance – squared value of the standard deviation

Why Psychologists Love the Normal Distribution

Useful mathematical features that form the basis for several kinds of statistical tests – many

tests require it!

It often arises spontaneously in nature (e.g., height, brain weight, IQ are normally

distributed)

Because it is precisely defined in mathematical terms, can calculate the area underneath

different regions of the curve with high levels of accuracy

Psychological Assessment - Lecture #4; Jan 29/13

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if it is normally distributed and you know you are 1 standard deviation over the mean, if you want to

know how many people are more neurotic than you, you add 13.59 + 2.14, if people are lower you add

all the numbers to the left from you, and you need to memorize the percentages (2.14%, 13.59%,

34.13%) from -2 to +2 there is 95.44% population is there, from -3 to +3 99.72% population is there,

from -1 to +1 there is 68.26% population there

## Document Summary

Based on one of the most well-validated and extensively studied models of normal personality functioning. Neuroticism - likelihood to experience negative emotions, high scores are worse to have. Extraversion - like social interactions, favour being social. Openness to experience - trying new things, flexible to your ideas. Conscientiousness - how diligent are you, are you going to get your work done on time? are you going to meet deadlines. Scores range from 1(disagree strongly) to 5 (agree strongly) Raw scores in isolation are absolutely meaningless that compares to other tests where a raw score can be meaningful. Become meaningful in relation (when you compare) to norms [compare score to a healthy person/ average ] Recall: norm-referenced tests - the way we interpret scores is based on how the normal person does, if it isn"t a norm test then it would be a criterion test (when you meet all the criteria)