MEDizzy - The number of falls that occurred in 9 Boston nursing homes

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Evidence-Based Medicine

The number of falls that occurred in 9 Boston nursing homes in November–April 2005 was reported as: 127, 104, 103, 81, 86, 117, 89, 97, and 95. What is the median number of falls among the nursing home residents?

ExplanationData are most commonly investigated at their center—where the observations have a tendency to cluster (ie, measures of central tendency). Three common measures of central tendency are mean, median, and mode (see following examples). To calculate the median in a set of data with n observations where n is odd, the median is the middle value ((n + 1)/2; in our case, since there are 9 observations, the mean is (9 + 1)/2 = 5). If n was even, the median is the average of the 2 middle values, that is, the average of observations (n/2) and (n/2) + 1. To find the median in our sample, first rank the observations: 81, 86, 89, 95, 97, 103, 104, 117, 127 Take the number of observations and add 1 because there is an odd number of observations and divide by 2 ([n + 1]/2 or [9 + 1]/2 = 5). The fifth-ranked number of falls, the median, is 97.