Even if you’re just a casual basketball fan, you nonetheless probably know that teams playing at home win way more often than they lose (this is true for other sports too). In chapter 9, we’ll explore the actual win-loss percentages between home and visiting teams under different permutations of prior days off, but in the meantime, we want to determine if there is an officiating bias that might explain home-court advantage. We’ll compare counts of foul calls and free throw attempts between home and visiting teams and then conduct statistical tests to determine if any variances in those counts are statistically significant and what their effect size may be. Which statistical tests to run mostly depends on the data. Because we’ll be comparing two groups (and just two groups) where the outcomes are numeric, our plan is to therefore run t-tests to determine whether or not any variances are statistically significant and Cohen’s d effect size tests to measure the size of those variances.