Speed skating is a sport in which it is important to have a suit that minimizes wind drag as much as possible, as the difference between winning and losing a race can be as small as a thousandth of a second. In the 2014 Winter Olympics, U.S. speed skaters used a suit called the Mach 39, and none medaled despite high expectation before the games. For the 2018 Winter Olympics, a new suit design called the H1 was developed. Suppose the designers wanted to test if skaters would be faster in the H1 or the Mach 39. They have 10 Olympic speed skaters and 10 recreational speed skaters on whom to test the suits.

a. Identify the treatment variable and the response variable.

b. Describe a simple randomized design (not blocked) to test whether the H1 suit decreases race times. Explain in detail how you will assign skaters to treatment groups.

c. Describe a blocked design using the types of skaters that could be used to test whether the H1 suit decreases race times. What advantage does the blocked design have?

d. Describe a design that uses the skaters as their own controls to reduce variation.