Continuing your discussion from Question #1 this week. What will be your decision rule for deciding to accept or reject the null? The decision rule is based on your critical value. Your critical value can be easily calculated in Excel. However you must first determine the confidence level you want to test at. This is at the discretion of the researcher based on the risk of accepting or rejecting the null in error. There are only three confidence levels used in research. These are 99%, 95%, and 90%. If you chose to test at a 90% confidence level this means that there is a 10% change that you could reject or accept the null in error. Therefore the probability (a or alpha) is 0.10.