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

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Psychological Assessment - Lecture #4; Jan 29/13
1
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]
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Psychological Assessment - Lecture #4; Jan 29/13
2
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
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Psychological Assessment - Lecture #4; Jan 29/13
3
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
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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)

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