I have used the Descriptive Statistics function built into Microsoft Excel to build this small table.

To derive these statistics (in Excel 2000: check other versions, but they'll be similar) from data series

Tools

... Data Analysis

... Descriptive Statistics

then, having chosen the data range and the output cell, select the Summary Statistics option I have also set the Kth largest and smallest values at 5: the 5th largest and the 5th smallest: set is, don't set it ... use it, don't use it ... it's up to you!

Descriptive Stats: Visits
Mean	20.6630
Standard Error	2.1099
Median	10.5000
Mode	4
Standard Deviation	20.2372
Sample Variance	409.5446
Kurtosis	0.9490
Skewness	1.2605
Range	81
Minimum	2
Maximum	83
Sum	1,901
Count	92
Largest(5)	66
Smallest(5)	2

I used the [arithmetic] mean value when I drew the Output Gap Type chart: I subtracted the mean from all of the actual values and derived the difference: positive, negative or zero. If it were necessary, I would have drawn similar graphs using the median and the mode: equally valid measure of "average" although their values are different from the mean.

Otherwise, I haven't used the data from this table except that I checked that the sum of 1,901 visitors is correct, the range seems valid and so on.

Duncan Williamson
3 November 2001