You want to distinguish if leptin effects on sperm counts are due to an alteration during puberty or development or due only to the effect of leptin on spermatogenesis. For this experiment, you decide to use bulls that are approaching retirement from use as semen providers. These bulls are all used to semen collection procedures. You collect semen samples for sperm counts on all bulls as well as blood for leptin levels. After measuring that all are similar, you divide the group in half. Half receive a device that continuously infuses them with leptin; the other half receive the same device, but it only infuses them with the carrier solution for the leptin (placebo). After 6 weeks of leptin infusion, you sample all the bulls again for both blood, measuring leptin levels, and semen, measuring sperm counts. a. What are the independent and dependent variables?
b. What statistical tests do you need to run first once you collected data on the bulls?
c. What would be the main statistical test would you use to analyze this data, assuming you proved normality?
d. What type of graph would you draw to illustrate the experiment?