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Descriptive Statistics Vocab
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Terms in this set (30)
Normal Distribution
Hypothetically represents the way test scores would fall if a particular test were given to every student for whom the test was designed (scores fall in the shape of a bell curve)
Ratio Scale
A scale that uses set units of measurement, has a true meaning of absolute-zero and can be used for direct comparison
Measures of Central Tendency
Methods for organizing and describing data to see how they cluster around the average score. Mean, Median and mode are examples
Derived Scores
Scores obtained by going to a conversion chart in the test manual. The raw score (# of correct answers) is translated into a score that allows us to make comparisons
Descriptive Statistics
Numbers that are used to summarize and describe sets of data
Frequency Distribution
How often each score occurs in a given set of data
Standard Score
Describes how a student performed on a test compared to a representative sample of students of the same age from the general population
Mode
The most frequently occurring score in a set of scores
Multimodal Distribution
When there are three modes (three scores which appear most often) in a given set of data
Variability
Difference in scores, how they vary
Bimodal Distribution
When there are two modes (two scores that appear most often) in a given set of data
Measures of Dispersion
How scores are spread from the mean (how far above or below the mean a score is)
Deciles
Data that is ranked and divided into 10 groups with each group representating 10% of the obtained scales
Variance
Describes the total amount that a group of scores vary in a set of data
Stanines
Used with group achievement test scores. Divide the scores into 9 groups with a mean of 5 and standard deviation of 2
Range
The Distance between the highest and lowest scores in a set of scores
Z-scores
A statistical measurement (uses standard deviation units of measurements) of a score's relationship to the mean in a group of scores (a score of 0 means the score is the same as the mean score)
Skewed
When scores are not distributed in a normal curve. Occurs when small or restricted populations are tested
Standard Deviation
A unit of measurement that represents the typical amount that a score can be expected to vary from the mean in a given set of data
Positively Skewed
When most of the scores fall (or are distributed) below the mean
Mean
The average of a set of data. One of the best ways to measure average performance
Negatively Skewed
When a large number of the scores occur above the mean
Median
The middle most score in a set of data
Percentile Ranks
Scores that express the percentage of students who scored as well as or lower than a given students score
Frequency Polygon
A graph with test scores represented on the horizontal axis an the number of occurrences represented on the vertical axis
Ordinal Scale
Numerical scale which uses numbers to rank order
Raw Score
The correct number of items a student receives on a test
Nominal Scale
Numbers used for identification purposes only
Norm-Referenced Test
Tests Designed to compare an individual's score with the national average
Interval Scale
A scale that uses set units of measurement for ranking order without an absolute-zero quality (example: thermometer)
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