Statistics Refresher Flashcards
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
Average deviation
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
Bar graph
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
Bimodal distribution
In a psychometric context, a set of test scores arrayed for recording or study
Distribution
A tabular listing of scores along with the number of times each score occurred
Frequency distributions
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
Frequency polygon
A diagram or chart composed of lines, points, bars, or other symbols that describe and illustrate data
Graph
A tabular summary of test scores in which the test scores are grouped by intervals; also referred to as class intervals
Grouped frequency distribution
A graph with vertical lines drawn at the true limits of each test score (or class interval), forming a series of contiguous rectangles
Histogram
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
Interquartile range
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
Interval scale
An indication of the nature of the steepness (peaked versus flat) of the center of a distribution
Kurtosis
A description of the kurtosis of a distribution where the distribution is relatively peaked in its center
Leptokurtic
A measure of central tendency derived by calculating an average of all scores in a distribution; a statistic at the ratio level of measurement
Mean
Assigning numbers or symbols to characteristics of people or objects according to rules
Measurement
A statistic indicating the average or middlemost score between the extreme scores in a distribution
Measure of central tendency
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
Median
A description of the kurtosis of a distribution where the distribution is not extremely peaked or flat in its center
Mesokurtic
A measure of central tendency derived by identifying the most frequently occurring score in a distribution; nominal in nature
Mode
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
Nominal scale
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
Normal curve
Conceptually, the end product of “stretching” a skewed distribution into the shape of a normal curve, usually through nonlinear transformation
Normalized standard score scale
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
Ordinal scale
A description of the kurtosis of a distribution where the distribution is relatively flat in its center
Platykurtic
One of three dividing points between the four quarters of a distribution, each typically labeled Q1, Q2, or Q3
Quartile
A descriptive statistic of variability derived by calculating the difference between the highest and lowest scores in a distribution
Range
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
Ratio 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
Scale
A measure of variability equal to the inter-quartile range divided by two
Semi-interquartile range
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
Skewness
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
Standard deviation
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
Standard score
A standard score derived from a scale with a mean of 5 and a standard deviation of approximately 2
Stanine
Named for Thorndike, a standard score calculated using a scale with a mean set at 50 and a standard deviation set at 10
T score
An indication of how scores in a distribution are scattered or dispersed
Variability
A measure of variability equal to the arithmetic mean of the squares of the differences between the scores in a distibution and their mean
Variance
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
z score
