Determining the optimum sample size for a particular study is, in some respects, very much an art. Many researchers forego complicated mathematical calculations to determine the right sample size to obtain a particular amount of statistical power (which leads to a certain level of confidence that the sample is statistically representative). These researchers usually use "rules of thumb" to determine the size sample they will need to represent a given population. Using such "rules" requires considerable experience with sampling -- something novice researchers just don't have. So, then, the problem becomes how to know the minimum number of subjects (or entities) to sample that will give a statistically representative sampling of the population.

To help you overcome your lack of sampling experience and to assist you in selecting an appropriately sized sample without going overboard (and thus costing you extra time and/or money in your own research), I have a couple of options for you on this page. The first option is a Sampling program I developed entitled (you guessed it) SAMPLE. There are two versions of the program, a version that operates in DOS or Windows 3.1 or earlier, and a version designed to operate in Windows 95, 98, 2000, NT4, or XP. Be sure to download the proper version for your computer. The program you download from this page (below) is a self-extracting file. Download it to a temporary directory on your computer. After downloading it, exit your browser, switch to the temporary directory you downloaded the program into, and double click your mouse on the program name to extract and install it. The DOS/Windows 3.1 version of the program will be installed as SAMPLE.EXE and will be stored in a folder named SAMPLE. If you want to extract the program into another directory, simply enter the directory name before you press the UNZIP or Install button.

The Windows 95/98/NT4/XP version of the program will be installed as SampleSize.EXE and will be stored in a folder of your choice (default is C:\Program Files\SampleSize.

After the program is installed, you may delete the self-extracting file to save space on your computer's hard drive.

The Windows 95/98/NT4/XP version of the program creates a program icon (World Globe) on your computer desktop when it installs, so all you have to do to run the program is to double-click on the icon. If you are running the DOS/Windows 3.1 version, you can operate the program by using the Program Manager to go to the appropriate directory and click on the SAMPLE.EXE program icon. The program should automatically expand to full screen. When you are ready to leave the program, press the ESC key. If the screen goes black and shows only a "C >" prompt, type EXIT and press the ENTER key to return to Windows.

When finished with the program, to exit from the DOS/Win 3.1 version of the program, press the ESC key. For the Win 95/98/NT4/XP version, click the Exit key or the "X" in the upper right corner of the program window.

Download the sampl.exe program here (for MS DOS and Windows 3.1 only).

Download the samplsiz.exe program here (for Windows 95, 98, 2000, NT4, & XP).

If you don't want to go through the trouble of downloading and extracting the SAMPLE.EXE program, you may use the Sample Size Estimator routine I developed especially for this course. There's nothing to download. Just link to the page and enter some information on the form provided. Then press a button to calculate your desired sample size. What could be easier???