The probability of experiment-wise error is explored. Overall, the experiment-wise error rate is directly related to the test-wise error rate--the alpha level set by researchers to curtail the existence of a Type I error. A Type I error occurs when a true null hypothesis is rejected in a given study or experiment. The experiment-wise error rate is a result of the increased possibility for Type I error; it emerges when several hypotheses are tested at the same alpha level within a single study. The experiment-wise error rate may be substantially above the alpha level used to test each hypothesis separately. A single sample chi square test, using coin tossing as an example, illustrates the implications of the inflated experiment-wise error rate. Two tables present the experimental data and an attachment includes a program for calculating experiment-wise error inflation rates. (SLD)