Measurement
Act of assigning numbers or symbols to characteristics of things according to rules.
Scale
Set of numbers whose properties model empirical properties of the object.
Discrete Scale
Scale that categorizes variables (males and females)
Continuous Scale
Scale that measures continuous variables and always involves error.
Error
Refers to collective influence of all of the factors on a test score of measurement beyond those specifically measures by the test.
Scales of Measurement
Nominal, Ordinal, Interval and Ratio
Nominal Scales
Involves classification and categorization.
Ordinal Scales
Involves classification by rank-ordering.
Ordinal Scales
Have no absolute zero point.
Interval Scales
Contain equal intervals between numbers
Ration Scales
Has equal intervals. Like height and weight.
Ratio Scales
Have true zero point.
Distribution
Set of test scores arrays for recording of study.
Raw Score
Unmodified accounting of performance.
Frequency Distribution
Number of occurrence of scores
Class Interval
Test-score intervals
Graph
Diagram of chart that describe and illustrate date.
Histogram
Vertical lines drawn at the true limits of each test scores.
Bar Graph
Used to refer to categorization.
Frequency Polygon
Expressed in continuous lines connecting the points where test scores or class intervals meet.
Measures of Central Tendency
Indicates the average or midmost score between the extreme scores in a distribution.
Arithmetic Mean
Is equal to the sum of observation, divided by the number of observation.
Median
Middle score in a tendency
Mode
Most frequently occurring score.
Variability
Refers to the spread of the scores within a distribution along with the central tendency.
Four Measures of Variablity
Range, Interquartile Range, Variance and Standard Deviation
Range
Difference between highest and lowest
Variance
The degree of spread within the distribution
Standard Deviation
A measure of how the average score deviates or spreads away from the mean.
Average Deviation
Rarely used measure of variablity
Standard Deviation
Measure of variability equal to the square root of the average squared deviations about mean.
Skewness
Indication of how measurement in a distribution are distributed.
Positive Skew
Few of the score fall at the high end of the distribution. Exam was too difficult.
Negative Skew
Few score fall at the low end of the distribution. Exam was too easy.
Kurtosis
Steepness of a distribution in its center.
Platykurtic
Relatively falt.
Leptokurtic
Relatively peaked.
Mesokurtic
Somewhere in the middle.