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| the act of assigning numbers or symbols to characteristics of things (people, events, whatever) according to rules. |
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| the collective influence of all of the factors on a test score or measurement beyond those specifically measured by the test or measurement. |
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| Simplest form of measurement. Involve classification or categorizatoin based on one or more distinguishing characteristics, where all things measured must be placed into mutually exclusive and exhaustive categories. E.g., male=1 female =0. Arithmetic operations that can be performed with this data include counting for the purpose of determining how many cases fall into each category and a resulting determination of proportion or percentages. |
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| 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, 7476 Oregon's Death with Dignity Act (ODDA), 6465 |
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| Also referred to simply as the mean, a measure of central tendency derived by calculating an average of all scores in a distribution. |
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| 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 |
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| 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 |
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| A distribution in which the central tendency consists of two scores, occurring an equal number of times, that are the most frequently occurring scores in the distribution, 82, 86 binary-choice item |
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| In a psychometric context, a set of test scores arrayed for recording or study, 78 |
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| instrument for measuring mechanical force |
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| A tabular listing of scores along with the number of times each score occurred, 78 |
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| 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, 8081 frequency recording |
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| A diagram or chart composed of lines, points, bars, or other symbols that describe and illustrate data, 8081 |
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| grouped frequency distribution |
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| Also referred to as class intervals, a tabular summary of test scores in which the test scores are grouped by intervals |
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| A graph with vertical lines drawn at the true limits of each test score (or class interval), forming a series of contiguous rectangles, 8081 |
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| 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, 88 |
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| A system of measurement in which all things measured can be rank-ordered into equal intervals, where every unit on the scale is equal to every other and there is no absolute zero point (which precludes mathematical operations on such data), 7576 |
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| An indication of the nature of the steepness (peaked versus flat) of the center of a distribution |
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| A description of the kurtosis of a distribution that is relatively peaked in its center |
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| In psychometrics, a process of changing a score such that (a) the new score has a direct numerical relationship to the original score and (b) the magnitude of the difference between the new score and other scores on the scale parallels the magnitude of differences between the original score and the other scores on the scales from which it was derived; contrast with nonlinear transformation, 9899 |
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| Also called the arithmetic mean, a measure of central tendency derived by calculating an average of all scores in a distribution, 80, 84, 86 |
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| measure of central tendency |
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| tendency One of three statistics 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, and the mode is a measure of central tendency that is nominal in nature |
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| A statistic indicating how scores in a distribution are scattered or dispersed; range, standard deviation, and variance are common measures of variability, 87 average deviation, 8889 interquartile and semi-interquartile ranges |
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| A measure of central tendency derived by identifying the middlemost score in a distribution |
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| A description of the kurtosis of a distribution that is neither extremely peaked nor flat in its center |
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| A measure of central tendency derived by identifying the most frequently occurring score in a distribution |
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| A curve or distribution of scores that has extreme scores below the mean that are atypical of the majority of scores. |
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| 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, 74, 76 |
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| transformation In psychometrics, a process of changing a score such that (a) the new score does not necessarily have a direct numerical relationship to the original score and (b) 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 |
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| 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 |
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| normalized standard score scale |
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| Conceptually, the end product of "stretching" a skewed distribution into the shape of a normal curve, usually through nonlinear transformation |
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| normalizing a distribution |
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| A statistical correction applied to distributions meeting certain criteria for the purpose of approximating a normal distribution, thus making the data more readily comprehensible or manipulable, 99 |
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| 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, 7476 |
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| A description of the kurtosis of a distribution that is relatively flat in its center, 92 |
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| A curve or distribution of scores that has extreme scores above the mean that are atypical of the majority of scores |
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| One of three dividing points between the four quarters of a distribution, each typically labeled Q1, Q2, or Q3, |
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| A descriptive statistic of variability derived by calculating the difference between the highest and lowest scores in a distribution, 87 |
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| 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, 7677 |
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| A straightforward, unmodified accounting of performance, usually numerical and typically used for evaluation or diagnosis, 78 RCRAS. See Rogers Criminal Responsibility Assessment Scale reacculturation, 490 |
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| (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, 72 |
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| range A measure of variability equal to the interquartile range divided by 2, 88 |
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| 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, 9192 |
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| 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, 8991 |
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| A raw score that has been converted from one scale into another, where the latter scale (1) has some arbitrarily set mean and standard deviation and (2) is more widely used and readily interpretable; examples of standard scores are z scores and T scores, 96 |
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| A standard score derived from a scale with a mean of 5 and a standard deviation of approximately 2, 9899 |
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| A standard score derived from a scale with a mean of 5 and a standard deviation of approximately 2, 9899 |
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| The area on the normal curve between 2 and 3 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, 93 |
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| An indication of how scores in a distribution are scattered or dispersed, 87 |
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| A measure of variability equal to the arithmetic mean of the squares of the differences between the scores in a distribution and their mean, 8990 |
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| A standard score derived by calculating the difference between a particular raw score and the mean and then dividing by the standard deviation; a z score expresses a score in terms of the number of standard deviation units that the raw score is below or above the mean of the distribution, 9697, 100, |
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