Statistics Refresher

Question 1

A measure of variability derived by summing the absolute value of all the scores in a distribution and dividing by the total number of scores

Answer 1

Average deviation

Question 2

A graphic illustration of data wherein numbers indicative of frequency are set on the vertical axis, categories are set on the horizontal axis, and the rectangle bars that describe the data are typically noncontiguous

Answer 2

Bar graph

Question 3

A distribution in which the central tendency consists of two scores occurring an equal number of times, both the most frequently occurring scores in the distribution

Answer 3

Bimodal distribution

Question 4

In a psychometric context, a set of test scores arrayed for recording or study

Answer 4

Distribution

Question 5

A tabular listing of scores along with the number of times each score occurred

Answer 5

Frequency distributions

Question 6

A graphic illustration of data wherein numbers indicating frequency are set on the vertical axis, test scores or categories are set on the horizontal axis, and the data are described by a continuous line connecting the points where the test scores or categories meet frequencies

Answer 6

Frequency polygon

Question 7

A diagram or chart composed of lines, points, bars, or other symbols that describe and illustrate data

Answer 7

Graph

Question 8

A tabular summary of test scores in which the test scores are grouped by intervals; also referred to as class intervals

Answer 8

Grouped frequency distribution

Question 9

A graph with vertical lines drawn at the true limits of each test score (or class interval), forming a series of contiguous rectangles

Answer 9

Histogram

Question 10

An ordinal statistic of variability equal to the difference between the third and first quartile points in a distribution that has been divided into quartiles

Answer 10

Interquartile range

Question 11

A system of measurement in which all things measured can be rank-ordered, where the rank-ordering contains equal intervals, every unit on the scale is equal to every other unit on the scale, and there is no absolute zero point; mathematical operations may not be performed on the data because of the absence of a true or absolute zero point

Answer 11

Interval scale

Question 12

An indication of the nature of the steepness (peaked versus flat) of the center of a distribution

Answer 12

Kurtosis

Question 13

A description of the kurtosis of a distribution where the distribution is relatively peaked in its center

Answer 13

Leptokurtic

Question 14

A measure of central tendency derived by calculating an average of all scores in a distribution; a statistic at the ratio level of measurement

Answer 14

Mean

Question 15

Assigning numbers or symbols to characteristics of people or objects according to rules

Answer 15

Measurement

Question 16

A statistic indicating the average or middlemost score between the extreme scores in a distribution

Answer 16

Measure of central tendency

Question 17

A measure of central tendency derived by identifying the middlemost score in a distribution; takes into account the order of scores and is ordinal in nature

Answer 17

Median

Question 18

A description of the kurtosis of a distribution where the distribution is not extremely peaked or flat in its center

Answer 18

Mesokurtic

Question 19

A measure of central tendency derived by identifying the most frequently occurring score in a distribution; nominal in nature

Answer 19

Mode

Question 20

A system of measurement in which all things measured are classified or categorized based on one or more distinguishing characteristics and placed into mutually exclusive and exhaustive categories

Answer 20

Nominal scale

Question 21

A bell-shaped, smooth, mathematically defined curve highest at the center and gradually tapered on both sides, approaching but never actually touching the horizontal axis

Answer 21

Normal curve

Question 22

Conceptually, the end product of “stretching” a skewed distribution into the shape of a normal curve, usually through nonlinear transformation

Answer 22

Normalized standard score scale

Question 23

A system of measurement in which all things measured can be rank-ordered, where the rank-ordering implies nothing about exactly how much greater one ranking is than another and there is no absolute zero point on the scale; most scales in psychology and education are ordinal

Answer 23

Ordinal scale

Question 24

A description of the kurtosis of a distribution where the distribution is relatively flat in its center

Answer 24

Platykurtic

Question 25

One of three dividing points between the four quarters of a distribution, each typically labeled Q1, Q2, or Q3

Answer 25

Quartile

Question 26

A descriptive statistic of variability derived by calculating the difference between the highest and lowest scores in a distribution

Answer 26

Range

Question 27

A system of measurement in which all things 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, and all mathematical operations can be performed meaningfully because a true or absolute zero point exists; few scales in psychology or education use this scale

Answer 27

Ratio scale

Question 28

(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

Answer 28

Scale

Question 29

A measure of variability equal to the inter-quartile range divided by two

Answer 29

Semi-interquartile range

Question 30

An indication of the nature and 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

Answer 30

Skewness

Question 31

A measure of variability equal to the square root of the averaged squared deviations about the mean; a measure of variability equal to the square root of the variance

Answer 31

Standard deviation

Question 32

A raw score that has been converted from one scale into another, the latter scale (1) having some arbitrarily set mean and standard deviation and (2) being more widely used and readily interpretable; examples of standard scores are z scores and T scores

Answer 32

Standard score

Question 33

A standard score derived from a scale with a mean of 5 and a standard deviation of approximately 2

Answer 33

Stanine

Question 34

Named for Thorndike, a standard score calculated using a scale with a mean set at 50 and a standard deviation set at 10

Answer 34

T score

Question 35

An indication of how scores in a distribution are scattered or dispersed

Answer 35

Variability

Question 36

A measure of variability equal to the arithmetic mean of the squares of the differences between the scores in a distibution and their mean

Answer 36

Variance

Question 37

A standard score derived by calculating the difference between a particular raw score and the mean, divided 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

Answer 37

z score