Psychological - W3 - Chapter 3 - DN Part 3
A platykurtic distribution has low kurtosis, meaning it is relatively flat at the center with fewer extreme outliers. Compared to a normal curve, it has lighter tails and a broader pea
platykurtic
a description of the kurtosis of a distribution that is relatively flat in its centre
p. 97
Key Terms
platykurtic
a description of the kurtosis of a distribution that is relatively flat in its centre
p. 97
positive skew
when relatively few of the scores fall at the high end of the distribution
positively skewed examination results may indicate the test was to...
quartile
one of the three dividing points between the four quarters of a distribution
each typically labelled
Q1
Q2
Q3
Q4
<...range
a descriptive statistic of variability
derived by calculating the difference between the highest & lowest scores in a distribution
...
rank-order/rank-difference correlation coefficient
an index of correlation
statistic of choice when
sample size is small, and
both sets of measurement are ordinal
also referr...
ratio scale
a system of measurement where all things being measured can be rank-ordered
the rank-ordering does imply something about exactly how much gre...
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| Term | Definition |
|---|---|
platykurtic | a description of the kurtosis of a distribution that is relatively flat in its centre p. 97 |
positive skew | when relatively few of the scores fall at the high end of the distribution positively skewed examination results may indicate the test was too difficult some easier questions would better discriminate at the lower end of the distribution p.97 |
quartile | one of the three dividing points between the four quarters of a distribution each typically labelled Q1 Q2 Q3 Q4 p.93 |
range | a descriptive statistic of variability derived by calculating the difference between the highest & lowest scores in a distribution p. 93 |
rank-order/rank-difference correlation coefficient | an index of correlation statistic of choice when sample size is small, and both sets of measurement are ordinal also referred to as the Spearman's rho p. 110-111 |
ratio scale | a system of measurement where all things being measured can be rank-ordered the rank-ordering does imply something about exactly how much greater one ranking is than another equal intervals exist between each number on the scale all mathematical operations can be performed meaningfully because a true zero point exists few scales in psychology & education use ratio scales p. 81-83 |
raw score | a straight forward, unmodified accounting of performance usually numerical typically used for evaluation or diagnosis |
scale | 1) a system of ordered numerical or verbal descriptors usually occurring at fixed intervals used as a reference standard in measurement 2) a set of numbers or other symbols whose properties model empirical properties of the objects or traits to which numbers or other symbols are assigned |
scatter diagram | a graphic description of correlation achieved by graphing the coordinate points for the two variables also referred to as a scatterplot scattergram, or bivariate distribution p.111 |
scattergram | a graphic description of correlation achieved by graphing the coordinate points for the two variables also referred to as scatterplot scatter diagram or bivariate distribution p.111 |
scatterplot | a graphic description of correlation achieved by graphing the coordinate points for the two variables also referred to as scatter diagram scattergram, or bivariate distribution p.111 |
semi-interquartile range | a measure of variability equal to the interquartile range divided by two p.94 |
skewness | an indication of the nature & extent to which symmetry is absent in a distribution a distribution is said to be skewed positively when relatively few scores fall at the positive end and skewed negatively when relatively few scores fall at the negative end p.96-97 |
Spearman's rho | an index of correlation statistic of choice when sample size is small, and both sets of measurement are ordinal also referred to as the rank-order correlation coefficient, and rank-difference correlation coefficient p.110-111 |
standard deviation | a measure of variability equal to the square root of the averaged squared deviations about the mean also equal to the square root of the variance p. 94-96 |
standard score | a raw score that has been converted from one scale into another the new scale has arbitrarily set M & SD is more widely used & readily interpretable examples of standard scores are z scores T scores |
stanine | a standard score derived from a scale with a mean of 5 and a standard deviation of approx. 2 p.103-104 |
T score | a standard score calculated using a scale with a mean set at 50 and a standard deviation set at 10 used by the developers of the MMPI named for Thorndike p. 103, 429 |
tail | the area on the normal curve between 2 and 3 standard deviations above the mean, and Answer: -2 and -3 standard deviations below the mean a normal curve has two tails p. 101 |
variability | an indication of how scores in a disrtibution are scattered or dispersed p. 92-96 |
variance | a measure of variability equal to the arithmetic mean of the squares of the differences between the scores in a distribution and their mean p.95, 146 |
z score | a standard score derived by calculating the difference between a particular raw score & the mean and then dividing by the standard deviation a z score expresses a score in terms of the number of standard deviation units the raw score is below or above the mean of the distribution p. 102-103 |