6. Measures of variability Consider a data set containing the following values: 70 65 71 78 89 68 50 75 The smallest value is 50 and the largest value is 89 Therefore, the range is 39 The first quartile is . The third quartile is . Therefore, the interquartile range (IQR) is The mean of the preceding values is 70.75. The deviations from the mean have been calculated: -0.75 -5.75 0.25 7.25 18.25 -2.75 -20.75 4.25 If this is sample data, the sample variance is , the sample standard deviation is If this is population data, the population variance is Suppose the smallest value of 50 is misrecorded as 5. The range would standard deviation would , and the coefficient of variation is , the population standard deviation is , the IQR would and the coefficient of variation is , and the variance and