Tony writes: > One of my collegues is working on a report to provide > feedback to a number of organisation that have provided data to us. > One of these statistics collected was how many weeks did it take > to fill a vacancy. In reporting this statistic back to the > organisations my collegue asked whether she should use the mean or the > median. The reply from her supervisor was "if the results are > normally distributed then use the mean otherwise use the median". I > am sure this is sage advice, but why?
One advantage of the mean that is often overlooked is that it extrapolates well to totals. Suppose for example, that each week of vacancy costs an organization $5000 and that our organization has had 20 vacancies in the past year. If we take the average weeks of vacancies times 20 times 5000 we would get an estimate of the total cost to the organization. You couldn't do that with a median. In medicine, the folks who do cost-benefit analyses almost always use a mean rather than a median (or a log transformation) even when the data is highly skewed because it helps the hospital, insurance company, etc. better understand the impact on their bottom line. Of course, there is no rule that says you can't report both a mean and a median. Steve Simon, [EMAIL PROTECTED], Standard Disclaimer. The STATS web page has moved to http://www.childrens-mercy.org/stats. . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
