collective influence of all of the factors on a test score or measurement beyond those specifically measured by the test or measurement.

z-score

being the first to refer to the curve as the normal curve

statistics that describe the amount of variation in a distribution

all scores are listed alongside the number of times each score occurred.

bell-shaped, smooth, mathematically defined curve that is highest at its center. ● the mean, the median, and the mode all have the same exact value.

standard score obtained that retains a direct numerical relationship to the original raw score.

may be required when the data under consideration are not normally distributed yet comparisons with normal distributions need to be made.

somewhere in the middle

meaning of X

sum

results from the conversion of a raw score into a number indicating how many standard deviation units the raw score is below or above the mean of the distribution.

t score

have categories with a clear and uncontroversial order ● measurements in which people are ranked (0-100)

equal to the interquartile range divided by 2.

relatively few of the scores fall at the high end of the distribution.

indicate that individual scores have been used and the data have not been grouped.

graph with vertical lines drawn at the true limits of each test score (or class interval), forming a series of contiguous rectangles. - X-axis (abscissa) - test scores to be placed (single scores or the midpoints of the class intervals) ● Y-axis (ordinate) - numbers indicative of the frequency of occurrence

act of assigning numbers or symbols to characteristics of things (people, events, whatever) according to rules

equal to the arithmetic mean of the squares of the differences between the scores in a distribution and their mean.

a number that provides us with an index of the strength of the relationship between two things. ● expresses a linear relationship between two (and only two) variables, usually continuous in nature.

frequently used when the sample size is small (fewer than 30 pairs of measurements) and especially when both sets of measurements are in ordinal (or rank-order) form.

a deviation about a mean of a distribution

the dividing points between the four quarters in the distribution are the, refers to a specific point

"the sum of"

relatively peaked

composed of a scale that ranges from 5 standard deviations below the mean to 5 standard deviations above the mean.

, when one variable increases while the other variable decreases.

expressed by a continuous line connecting the points where test scores or class intervals (X-axis) meet frequencies (Y-axis).

simplest form of measurement ● involve classification or categorization, where all things measured must be placed into mutually exclusive and exhaustive categories.

value indicating how much variance is shared by two variables (X and Y) being calculated

takes into account the actual numerical value of every score.

a straightforward, unmodified accounting of performance that is usually numerical.

the values can be any real number in the scale’s sample space.

values indicate a distribution with a rounded peak and thinner tails.

statistic used to express the strength of the relationship or the magnitude of the differences in data

best to round continuous scales

has a true zero point, which indicates the absence of the thing being measured

absence of a quantity

most commonly used measure of central tendency

is a measure of variability equal to the difference between Q3 and Q1.

test-score intervals, also called class intervals, replace the actual test scores.

a set of test scores arrayed for recording or study.

statistic that indicates the average or midmost score between the extreme scores in a distribution.

the nature and extent to which symmetry is absent. ● indication of how the measurements in a distribution are distributed.

middle score in a distribution

x-axis

upper limits of the distribution

refers to an interval

there are two scores that occur with the highest frequency (of two).

relatively flat

family of techniques used to statistically combine information across studies to produce single estimates (effect size) of the data under study.

“add all the test scores.”

- most frequently occurring score in a distribution of scores ● not a very commonly used measure of central tendency.

y-axis

, characterized by a high peak and “fatter” tails compared to a normal distribution.

steepness of a distribution in its center

moments squared

the moments cubed, and so forth

area on the normal curve between 2 and 3 standard deviations above the mean.

statistical tool of choice when the relationship between the variables is linear and when the two variables being correlated are continuous

meaning that it approaches, but never touches, the axis

the values that a variable can take on.

other name for normal curve

, normalizing a distribution involves “stretching” the skewed curve into the shape of a normal curve and creating a corresponding scale of standard scores

set of numbers (or other symbols) whose properties model empirical properties of the objects to which the numbers are assigned.

negative skew

emphasized that what he tried to do with his test to classify (and rank) people.

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

an instrument used to measure strength of hand grip

lower limits of the distribution

individual deviations about the mean of a distribution

another tool that could be used to describe the amount of variability in a distribution

, an “eyeball gauge” of how curved a graph is

equal to the difference between the highest and the lowest scores.

, defined as professional practice that is based on clinical and research findings ● Methods, protocols, techniques, and procedures, used by professionals, that have a basis in clinical and research findings

extremely atypical point located at a relatively long distance—an outlying distance—from the rest of the coordinate points in a scatterplot

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

ameasureofvariabilityequalto the square root of the average squared deviations about the mean. ● equal to the square root of the variance

quarter-points in a distribution of scores.

a raw score that has been converted from one scale to another scale, where the latter scale has some arbitrarily set mean and standard deviation.

a term that was a contraction of the words standard and nine. ● a standard score with a mean of 5 and a standard deviation of approximately 2, divided into nine units

meaningful distances between numbers, each unit on the scale is exactly equal to any other unit on the scale. ● possible to add and subtract scores, which allows for calculating means and standard deviations

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

if a correlation is zero, then absolutely no relationship exists between the two variables

simple graphing of the coordinate points for values of the X-variable (placed along the graph’s horizontal axis) and the Y-variable (placed along the graph’s vertical axis). ● they provide a quick indication of the direction and magnitude of the relationship, if any, between the two variables.

most frequently used level of measurement in psychology

, two variables simultaneously increase or simultaneously decrease, then those two variables are said to be

one graphic representation of data of particular interest to measurement professionals

expression of the degree and direction of correspondence between two things.

has a sample space that can be counted.