Volunteers who had developed a cold within the previous 24 hours were randomized to take either zinc or placebo lozenges every 2 to 3 hours until their cold symptoms were gone (Prasad et al. 2000). Twenty-five participants took zinc lozenges, and 23 participants took placebo lozenges. The mean overall duration of symptoms was found for each group.
a. What is the parameter of interest in this situation? Give notation and define it.
b. What is the sample statistic in this situation? Give notation and define it.
c. What condition(s) must be met for the sampling distribution of the statistic you defined in part (b) to be approximately normal?