Measures of Central Tendency & Variability
The value that appears most often in a data set
Mode
The degree to which an instrument is free from measurement error; Consistency
Reliability
A bell-shaped curve which shows the probability distribution of a continuous random variable. The total area under the ___ logically represents the sum of all probabilities for a random variable.
Normal Distribution/Curve
Type of test that measures a person's performance in comparison to the performance of a larger group; usually a statistically selected group of test takers, typically of the same age or grade level, who have already taken the test
Norm-referenced tests
The difference between the lowest value and the highest value
Range
The degree to which an instrument measures the constructs it intends to measure
Validity
A type of calculated standardized score which helps you compare scores easily. A score of 50 represents the mean. A difference of 10 from the mean indicates a difference of one standard deviation.
T-Scores
A method of sampling from a population which can be partitioned into sub-populations, such as race, class, gender, or level of education
Stratified Sampling
The middle number in a list of numbers ordered from lowest to hightest
Median
the extent to which a test is subjectively viewed as covering the concept it intends to measure; the transparency or relevance of a test as it appears to test participants
Face Validity
a range of values so defined that there is a specified probability (90-95% is gold standard) that the true value lies within it
Confidence Intervals
A result that's not attributed to chance. More technically, it means that if the Null Hypothesis is true (which means there really is no difference), there's a low probability of getting a result that large or larger.
Statistical Significance
the total of all the values, divided by the number of values
Mean
the degree in which the scores on a measurement are related to other scores on other measurements that have already been established as valid
Concurrent Validity
The percentage of scores in its frequency distribution that are equal to or lower than it. For example, a test score that is greater than 75% of the scores of people taking the test is said to be at the 75th ___ .
Percentile
An idea or theory containing various conceptual elements, typically one considered to be subjective (ex. behavior, personality, etc.)
Construct
A measure of the amount of variation or dispersion of a set of values. On the low side, it indicates that the values tend to be close to the mean of the set, while on the high side, it indicates that the values are spread out over a wider range.
Standard Deviation
the extent to which the underlying supposed structure of a scale is recoverable in a set of test scores; determined via factor analysis (structural equation modeling)
Factorial Validity
A measure of how much measured test scores are spread around a “true” score; directly related to a test’s reliability: The larger the ___, the lower the test’s reliability; Used to calculate confidence intervals
Original data that has not been transformed; Without knowing how many questions were on the test or the point value of each question, ___ are impossible to decipher in terms of percentile, grade, or measured progress.
Raw Scores