Designing Trials Efficiently: Review of Sample Size Considerations Part 2.

Sample size is essentially the number of research participants or volunteers that you need to participate in your study. And I use that terminology because first of all, it's not always right to refer to them as patients. If you're doing a survey on totally healthy people, they're not patients. Remember, "patients" comes from the Greek word

meaning "to suffer." Those people aren't suffering. You may just want to interview people who are out there in the wider community as to why they get a flu vaccine or not. Those people aren't sick. They're not patients. And the second thing is, for these research studies, people are really -- you have to really on the altruism of folks

who sign up to volunteer to be a participant in a study. So, always keep in mind that these people are research volunteers. They're helping you out by being in the study. So, many variables have what's called a normal distribution or the famous bell-shaped curve that we all learned about in grade school when we were getting As, Bs, Cs, and Ds.

So, what that means is that many data falls onto this kind of bell-shaped curve where 95 percent of the data's in the middle, and there's 2.5 percent of the data on what's called the tails of this curve. So, if I took, for instance, the height of people in this room, there would be an average height, and then there would be some distribution.

So, if Danny DeVito walks in and Shaquille O'Neal walks in, what's going to happen is this curve is going to get broader because we're going to have people on one end and another person on way far on the other hand. So, keep that in mind when we talk about homogeneity in the data.