Sample Size

Sample size calculation is one of the crucial steps in statistical analyses. The extraction of the sample size is generally a tedious process in the preparation of a particular statistical study.

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The statistical studies that consist of various kinds of surveys, experiments, observational studies, etc. always give valid conclusions only if they are appropriately and significantly planned by keeping certain things in mind. These things include the reliability of the instruments to be used for measuring, the appropriate understanding of the problem, and the determination of an adequate sample size.

Because type II errors are generally committed by the researcher due to inadequate sample size, some clinical trial sample size calculation programs have been developed. This sample size calculation program has been specifically designed in order to avoid Type II errors which are a serious kind of error, especially in the field of medicine.

The sample size program can be downloaded from some clinical related websites. This sample size calculation program also has certain programs which can be used for computing the group sequential boundaries. The sample size calculation program is generally located in the bottom half of the window that is downloaded from the clinical website.

The sample size program is generally written in the form of java programming language. This means that the sample size determination program can run on any kind of computer provided if it has the java runtime environment (JRE). Generally, MS Windows has the java runtime environment (JRE) enabled in them and the sample size.jar file can be directly executed from window explorer.

JRE can be downloaded with the help of some java related websites. After that is complete, one can run sample size calculation programs on the computer. The sample size calculation program can also be run in a non MS windows using the command prompt “java-jar sample size.jar.”

The sample size calculation program consists of a file menu which has three tabs, namely dichotomous, continuous and survival.

The sample size calculation program for the dichotomous type of response has variables like ‘yes or no,’ ‘heads and tails,’ ‘presence or absence,’ etc. In the sample size calculation program, it is assumed that the user who will be working on the sample size calculation should be well versed with the different parameters.

There is also a calculate button in the screen of the sample size calculation program. This button can help the user to perform different sorts of sample size calculations, like calculate power, etc. In the case where the sample size calculation is not possible, then it warns the user with a popup message, and thus no calculation will be performed.

For the sample size calculation program for the continuous response variables, the screen is divided into two halves.

In the one half there is sample size calculation, and in the other half there is the saved results. The user using the sample size calculation program can provide the values in any open cells in the calculation section. Similar to the dichotomous case, if the sample size calculation is not possible, then the warning message of “no calculation” appears on the screen as a popup message.

In the case of survival, the sample size calculation program is done on those kinds of variables where the primary variable is the occurrence of some event.