We can anticipate that "weeks to fill a position" will be Poisson distribtured - they can't get less than 0, and could stretch out considerable. A.k.a., log-Normal distributed if you count fractions of weeks.
Use of an _average_ for this data will give extra weight to those long to fill positions, and possibly distort the reported value - making it "mean" less to the receiver. If you take the log (natural or base 10) of the time-to-fill, it may well appear as a Normal dist. (in the transformed condition) and then an average would have more meaning (after you take the exponent of the average. If this path to a solution gives you the willies, then taking a median will reduce the impact of a long hold out position, even though it is still not what the reader thinks of of by "average." The core problem is that when we read "average" we often think in terms of a Normal distribution, and expect the data to cluster near that average. A Poisson dist. doesn't cluster there, so the meaning of 'average' isn't what the reader thinks it is. Cheers, Jay > Hi, > > 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? I would have thought that if the distribution was normally > distributed then the mean and the median would be roughly similar > figures since the normal curve has the frequency distributed around > the mean. My further thinking about this was that for any > distribution the mean will always be the upper bound of the median. > Is this correct? > . > . > ================================================================= > Instructions for joining and leaving this list, remarks about the > problem of INAPPROPRIATE MESSAGES, and archives are available at: > . http://jse.stat.ncsu.edu/ . > ================================================================= > -- Warner Consulting, Inc. 4444 N. Green Bay Road Racine, WI 53404-1216 Ph: (262) 634-9100 email: [EMAIL PROTECTED] Home of the A2Q Method(tm) What do you want to improve, Today! via CoreComm Webmail. http://home.core.com . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
