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Measuring Spread: Range, IQR, Standard Deviation

  • Range is the simplest way to calculate the spread of a distribution. It is also extremely influenced by outliers.

  • Before calculating the standard deviation, calculate the variance. Make sure whether you need to find the population variance and standard deviation or a sample variance or standard deviation.

  • Before calculating the interquartile range, make sure that the data are ordered from lowest to highest.

  • The standard deviation is the best measure of spreads since it uses all of the observations; however, if the data are skewed, the interquartile range is the preferred measure of the center.

Measuring Spread: Range, IQR, Standard Deviation

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

Mathematics: AP Statistics