Analytic Resources

Variability

In addition to knowing the "typical" score, you also want to know the spread, diversity, or similarity of the information in your data.

Measures of Dispersion (Spread)

CrashCourse: Measures of Spread (11:46)

StatTrek- How to Measure Variability

Statisticians use summary measures to describe the amount of variability or spread in a set of data.

The most common measures of variability are the range, the interquartile range (IQR), variance, and standard deviation.

Variance of a population (8:04)- P1

Variance of a population (12:22)- P2

Review and intuition why we divide by n-1 for the unbiased sample variance (video) | Khan AcademyReviewing the population mean, sample mean, population variance, sample variance and building an intuition for why we divide by n-1 for the unbiased sample variance

Simulation showing bias in sample variance (video) | Khan AcademySimulation by Peter Collingridge giving us a better understanding of why we divide by (n-1) when calculating the unbiased sample variance. Simulation available at: http://www.khanacademy.org/cs/challenge-unbiased-estimate-of-population-variance/1169428428

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