# Research Psych

 Measure of Variability Measures of variability describe the extentto which scores in a distribution differ from each other The Range The range indicates the distancebetween the two most extreme scores in a distribution Variance and Standard Deviation two measures of variability that indicatehow much the scores are spread out around the mean •We use the mean as our reference point sinceit is at the center of the distribution SampleVariance / Sample Standard Deviation sample variance is the average of the squared deviations ofscores around the sample mean ﻿﻿Formula: Computational Formula: Population Variance Formula Population Standard Deviation Formula Estimated Population Variance By dividing the numerator of the samplevariance by N - 1, we have an unbiasedestimator of the population variance Formula: Estimated Population Variance Computational formula Estimated Population Standard Deviation By dividing the numerator of the samplestandard deviation by N - 1, we have an unbiasedestimator of the population standard deviation. Formula Unbiased Estimators 1. 2. Quantity N-1 is called the degrees of freedom Proportion of Variance Accounted For proportion of variance accounted for is the proportion oferror in our predictions when we use the overall mean to predict scores that is eliminated when we use the relationship with another variable to predict scores AuthorAnonymous ID8349 Card SetResearch Psych DescriptionPsych Exam Updated2010-02-27T19:49:06Z Show Answers