1.4 Split summary stats results by groups

To run summary statistics on your variables separately for multiple groups of data, just choose a factor by which you would like to split the data in the dialog. For example, for the Ekofisk dataset, suppose we wished to obtain summary statistics (means and standard errors) separately for each of the 'Distance' groups. We can achieve this by choosing Tools > Summary Stats... > (Summarise > $\bullet$Variables) & (Split by > $\checkmark$Factor > Dist) & (Statistics > $\checkmark$Average & $\checkmark$Standard Error), as shown in the dialog below:

By default, PRIMER will provide the output for each summary statistic you have asked for as a separate data sheet, and the groups (corresponding to levels of the factor by which you have chosen to do the splitting), will be the 'Samples'. In the present example, you will see that the averages for each variable for the four distance groups (A, B, C, D) have been provided in 'Data2' and the standard errors are given in 'Data3'. There will be as many new data sheets generated as there are summary statistics asked for in the dialog. Note that the name of the summary statistic provided in each sheet is given in the title at the top of the sheet, e.g., 'Ekofisk oilfield macrofauna -Summary Statistics, Average'.

An alternative output format can be requested here, with results for different groups given on different sheets. To do this, choose Tools > Summary Stats... > (Summarise > $\bullet$Variables) & (Split by > ($\checkmark$Factor > Dist) & (Output > $\checkmark$Levels/groups as separate sheets)) in the dialog, like so:

Doing this yields a separate sheet of summary statistics for each of the groups (e.g., 'Data4' has all of the summary statistics you requested calculated for group D only, 'Data5' has the results for group C, and so on (see below). Note that, for this alternative type of output, the name of the factor on which the split was done and the specific group (factor level) is given in the title at the top of each new data sheet of results; for example, 'Ekofisk oilfield macrofauna -Summary Statistics, Dist: A'.