The chi squared (c-squared) test is one of the most important tests in statistics. It tests whether the observed frequencies in a distribution differ significantly from the frequencies which might be expected according to some ‘assumed hypothesis’.
QuickChi is a programme for carrying out c-squared tests. The default contingency table size is 2x2. Enter data into the boxes initially labelled A-D and click the ‘Calculate’ button. The programme calculates the value of c-squared (chi), the value of phi (the square root of chi/total) and then gives you the probability that this value of c-squared could arise by chance. A probability of <0.05 is regarded as statistically significant. Further data sets can be entered and results for all the tests are retained and listed in the results box. More complicated contingency tables up to 2x5 can be analysed by selecting the desired size in the pop-up menu labelled 2xn. Further data entry boxes will then appear.
The labels for the rows and colums can be edited if required by clicking on them.
When data have been entered it is possible to print the data values together with the results of c-squared tests using Print from the File menu. You can also save the data and results in a TEXT file by selecting Save from the File menu. This file is saved as a BBEdit file but can be opened by any word-processing programme so it can be formatted as you wish.
That's about it. This 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 6.1. and 7.5.3.
Version history
Version 1 - first release for 2x2 c-squared tests, Nov 1997
Version 1.0.1 - fixed a bug whereby not all data fields were checked for expected frequencies being sufficiently high
Version 1.1 - now analyses contingency tables up to a maximum of 2x5
If you use QuickChi you might also be interested in my other statistical programmes.
QuickTTest is a statistics programme for calculating means±SEM/SD and for performing Student’s t-test. Its main advantage over other programmes is that it allows you to enter the data for t-test analysis not only as individual values but also as pre-calculated Mean±SEM or Mean±SD.
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.
The programmes can be obtained from the Info-Mac archives or downloaded directly from my Web Page (http://www.ndcb.ox.ac.uk/sjha_progs.html).
