CombiStat is a programme that lets you carry out two useful statistical procedures. Firstly, you can combine several Mean±SEM values into an overall Mean±SEM. Secondly, you can calculate the SEM and SD of a ratio when both the numerator and the denominator have an associated SEM.
When the programme opens you are presented with the Combining means±SEM window. Enter the values for Mean, SEM, and n in the Input boxes and click Add to enter the first set of values. These are shown in the Data summary box. Continue entering more values for the first dataset. The combined mean,SEM and n values are shown in the Combined values boxes which are updated after each set of values. When all the values for the first dataset are entered, clicking Store saves the data values and displays the combined values in the Results summary box. Further datasets can then be entered.
From the Options menu you can select the Statistics of a ratio mode. Enter the appropriate values for the numerator and denominator values into the boxes and click Calculate to get the value of the ratio of Numerator/Denominator and the associated SEM and SD which are displayed in the Results summary box. Further data can be entered and saved similarly.
In either mode, the number of decimal places used for the calculations can be selected from the Decimal places pop-up menu. The default value is 3.
From the File menu you can Print the entered data and the results summary. You can also Save the values to a file for editing. The file is saved as a BBedit file but as it is a TEXT file it can be opened in any word processor.
That's about it. CombiStat is freeware. If anyone tries the programme and finds it useful, I'd be pleased to receive an email or postcard. Suggestions for improvement are encouraged. Any bug reports would also be welcomed - so far I have had no problems running under System 7.5.3 and 7.6.1.
If you use CombiStat you might also be interested in my other statistics programmes - QuickTTest is a programme for calculating means±SEM/SD and for performing Student’s t-test. QuickChi is a programme for carrying out a 2x2 Chi Squared test. These can be obtained from the Info-Mac archives or downloaded directly from my Web Page (http://www.ndcb.ox.ac.uk/sjha_progs.html).
