Summary Statistics

Use the Geochem Analysis > Summary Statistics menu option (CHSTAT GX), to calculate the summary statistics of a selected channel.

Summary Statistics dialog options

Channel

Select a channel from the current database.

Mask channel

Select a mask channel from the drop-down list. If the use of the mask channel is enabled and set to this channel, only those data values whose corresponding mask channel values are not dummy values will be plotted or exported.Channels must have their CLASS attribute set to MASK to appear as selections in the drop-down list. If the mask channel does not exist, it will be created with its CLASS attribute set to MASK. The default mask channel is set from the CHPREFERENCES GX (Geochem Map > Preferences...).

Application Notes

Click on the [Show Stats] button to display the Summary Statistics of the selected channel. The Summary Statistics include: Element, Number of items, Number of Dummies, Minimum, Maximum, Range, Mean and Standard Deviation.

Click on the More button on the Summary Statistics dialog box to display the Advanced Statistics of the selected channel. The Advanced Statistics include: Element, Number of Items >0, Geometric Mean, Sum, Sum of squares, Variance, Standard Deviation, Standard Error, Mean, Median, Mode, Skewness, Kurtosis.

Definitions and Formulas

Various different formulas exist for specific statistics to adjust for bias introduced by sampling. We use the "N-1" versions of the standard deviation, skew and kurtosis. The kurtosis is the "excess kurtosis", and subtracts off the factor of 3 giving zero for normally-distributed data.