Random numbers demonstrate the frequency of type I errors: Three spreadsheets for class instruction

This paper describes three spreadsheet exercises demonstrating the nature and frequency of type I errors using random number generation. The exercises are designed specifically to address issues related to testing multiple relations using correlation (Demonstration I), t tests varying in sample size (Demonstration II) and multiple comparisons using analysis of variance (Demonstration III). These demonstrations highlight the purpose and application of hypothesis testing and teach students the dangers of data dredging and a posteriori hypothesis generation.