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Measurement 3
flashcards from Psychological measurement and assessment 6th ed. website
41
Psychology
Undergraduate 4
01/09/2012

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Term
Arithmetic mean
Definition
Also referred to simply as the mean, a measure of central tendency derived by calculating an average of all the scores in a distribution
Term
Average deviation
Definition
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
Term
Bar graph
Definition
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
Term
Bimodal distribution
Definition
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
Term
Distribution
Definition
In a psychometric context, a set of test scores arrayed for recording or study
Term
Error
Definition
Collectively, all of the factors other than what a test purports to measure that contribute to scores on the test; error is a variable in all testing and assessment
Term
Frequency distributions
Definition
A tabular listing of scores along with the number of times each score occurred
Term
Frequency polygon
Definition
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
Term
Graph
Definition
A diagram or chart composed of lines, points, bars, or other symbols that describe and illustrate data
Term
Grouped frequency distribution
Definition
A tabular summary of test scores in which the test scores are grouped by intervals; also referred to as class intervals
Term
Histogram
Definition
A graph with vertical lines drawn at the true limits of each test score (or class interval), forming a series of contiguous rectangles
Term
Interquartile range
Definition
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
Term
Interval scale
Definition
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 interval-level data because of the absence of a true or absolute zero point
Term
Kurtosis
Definition
An indication of the nature of the steepness (peaked versus flat) of the center of a distribution, 82-83 See also Platykurtic, Leptokurtic, and Mesokurtic
Term
Leptokurtic
Definition
A description of the kurtosis of a distribution where the distribution is relatively peaked in its center
Term
Linear transformation
Definition
In psychometrics, a process of changing a score such that the new score has a direct numerical relationship to the original score, and the magnitude of the difference between the new score and the other scores on the scale parallels the magnitude of differences between the original score and the other scores from which it was derived; contrast with nonlinear transformation
Term
Mean
Definition
Also called the arithmetic mean, a measure of central tendency derived by calculating an average of all scores in a distribution
Term
Measure of central tendency
Definition
A statistic indicating the average or middlemost score between the extreme scores in a distribution. The mean is a measure of central tendency and a statistic at the ratio level of measurement; the median is a measure of central tendency that takes into account the order of scores and is ordinal in nature; the mode is a measure of central tendency that is nominal in nature
Term
Measure of variability
Definition
A statistic indicating how scores in a distribution are scattered and dispersed; range, standard deviation, and variance are common measures of variability
Term
Measurement
Definition
Assigning numbers or symbols to characteristics of people or objects according to rules
Term
Mesokurtic
Definition
A description of the kurtosis of a distribution where the distribution is not extremely peaked or flat in its center, 83 See also Kurtosis
Term
Nominal scale
Definition
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
Term
Nonlinear transformation
Definition
In psychometrics, a process of changing a score such that the new score does not necessarily have a direct numerical relationship to the original score, and the magnitude of the differences between the new score and the other scores on the scale may not parallel the magnitude of differences between the original score and the other scores on the scales from which the original score was derived; contrast with linear transformation
Term
Normal curve
Definition
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
Term
Normalized standard score scale
Definition
Conceptually, the end product of "stretching" a skewed distribution into the shape of a normal curve, usually through nonlinear transformation
Term
Ordinal scale
Definition
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
Term
Platykurtic
Definition
A description of the kurtosis of a distribution where the distribution is relatively flat in its center
Term
Quartile
Definition
One of three dividing points between the four quarters of a distribution, each typically labeled Q1, Q2, or Q3
Term
Ratio scale
Definition
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 are ratio scales
Term
Raw score
Definition
A straightforward, unmodified accounting of performance, usually numerical and typically used for evaluation or diagnosis
Term
Scale
Definition
(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
Term
Semi-interquartile range
Definition
A measure of variability equal to the inter-quartile range divided by two
Term
Skewness
Definition
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
Term
Standard deviation
Definition
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
Term
Standard score
Definition
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
Term
Stanine
Definition
A standard score derived from a scale with a mean of 5 and a standard deviation of approximately
Term
Tail
Definition
Tail The area on the normal curve between two and three standard deviations above the mean and the area on the normal curve between -2 and -3 standard deviations below the mean; a normal curve has two tails
Term
T score
Definition
Named for Thorndike, a standard score calculated using a scale with a mean set at 50 and a standard deviation set at 10; the measure of choice for the developers of the MMPI (As technical problems emerged in the scoring of MMPI protocols with T scores, some researchers suggested that these scores be replaced with normalized T scores; ultimately the developers of the MMPI-2 agreed to use what they called a uniform T score or UT)
Term
Variability
Definition
An indication of how scores in a distribution are scattered or dispersed
Term
Variance
Definition
A measure of variability equal to the arithmetic mean of the squares of the differences between the scores in a distribution and their mean
Term
z score
Definition
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
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