® ASHRAE
® ASHRAE
Dave Shipley created a simple spreadsheet to help estimate an appropriate experimental sample size for one of the work statements we were helping to develop. It is provided here as a free download, with no restrictions on its use. The file is a self-extracting Zip file--just "run" it by double-clicking on it to get it to extract. The Zip file contains one Excel file called "samplesizecalculator.xls".
This spreadsheet is designed to calculate the sample size required to obtain statistically valid results from an experiment comparing two sample groups. It is not designed to help with sample sizes for comparing more than two groups of samples.
To use the program, answer the seven questions on the "Questions and Answers" sheet. Each of the spaces where an answer is needed is coloured yellow. The number of samples required in each sample group appears at the bottom of the sheet. Each group must have at least that number of samples.
The author has locked all the cells in the spreadsheet except for the yellow ones on the Questions and Answers sheet. This is just to prevent errors in data entry. There is no password required to unlock them and make changes.
It is still wise to have your experimental design reviewed by someone who is knowledgeable about statistics, to avoid wasting time and money collecting data that will not satisfactorily answer your research questions.
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