Statistical Sciences 1024A/B Chapter Notes - Chapter 2: Quartile, Umber, Interquartile Range
20 Apr 2017
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The most common measure of centre is the arithmetic average, or mean. To calculate the mean, simply add together all the values of the observations, then divide by the total number of observations. Because the mean cannot resist the influence of extreme observations, it is not a resistant measure of centre. Another common measure of centre is the median. The median is the midpoint of a distribution, the number such that of the observations are smaller and the other are larger. To find median of a distribution: arrange all observations from smallest to largest. If the number of observations is odd, the medium is the centre observation in the ordered list. The mean and median measure centre in different ways, and both are useful. The mean and median of a rough symmetric distribution are close together. If the distribution is exactly symmetric, the mean and median are exactly the same.
