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Variability - Coggle Diagram
Variability
Variance
The mean of the squared deviations, or the average squared distance from the mean
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Population Variance is represented by the symbol lower case sigma and equals the mean squared distance from the mean. Population variance is obtained by dividing the sum of squares by N.
Sample Variance is represented by the symbol s^2
and equals the mean squared distance from the mean. Sample variance is obtained by dividing the sum of squares by n − 1
For a sample of n scores, the degrees of freedom, or df , for the sample variance are defined as df. The degrees of freedom determine the number of scores in the sample that are independent and free to vary
Standard Deviation
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Standard deviation is the square root of the variance and provides a measure of the standard, or average distance from the mea
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Sample standard deviation is represented by the symbol s and equal the square root of the sample variance
Variability provides a quantitative measure of the differences between scores in a distribution and describes the degree to which the scores are spread out or clustered together
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Biased vs. Unbiased
A sample statistic is biased if the average value of the statistic either underestimates or overestimates the corresponding population parameter
A sample statistic is unbiased if the average value of the statistic is equal to the population parameter.
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