Bonferroni Correction

When the same dependent variable is used multiple times in analysis it increases the likelihood of committing a Type 1 error.  Type 1 error occurs when a researcher incorrectly rejects a true null hypothesis.  To correct for this type of error, a Bonferroni type adjustment is typically made.  This is done by dividing the alpha level (typically set at .05) by the number of tests (n).  In this example we will assume three analyses use the same dependent variable.  The standard alpha level of .05 would be divided by three (number of analyses for each DV) and the new alpha level would be established at .017. This level would be used to determine statistical significance for the corresponding analyses (Tabachnick & Fidell, 2012).