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Lecture 4

Lecture 4.docx

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Anthony Ruocco

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Psychological Assessment - Lecture #4; Jan 29/13 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] 1 Psychological Assessment - Lecture #4; Jan 29/13 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 2 Psychological Assessment - Lecture #4; Jan 29/13 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 3 Psychological Assessment - Lecture #4; Jan 29/13 -the side that it is being pulled; so if being pulled on left side then it would be negatively skewed, and vice versa Is the Neuroticism Scale Normally Distributed in our Class? normal Is the Agreeableness Scale Normally Distributed in our Class? more on the right side Raw Score Transformations  Percentiles and percentile ranks  Standard scores  T-scores and other standardized scores 4 Psychological Assessment -
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