A Customer Services Strategy Manager for a National Wellbeing and Fitness

A customer services strategy manager for a national wellbeing and fitness company is interested in assessing customer usage of their gyms across 20 sites nationally. Different gym managers have collected and analysed data from each of the sites but the resultant twenty reports showed differing p-values, some sites found a statistical significance between increased opening hours of gyms and usage and others did not. Which of the following would it be useful for her to review?

A) Levels of missing data
B) Confidence intervals
C) Outliers
D) The Null Hypotheses