Question

a large study of 3000 canadian children and their mothers found that the children of mothers who drank diet soda daily during pregnancy were twice as likely to be overweight at age 1 as children of mothers who avoided diet soda during pregnancy.
you have 300 pregnant mothers who are willing to serve as subjects in an experiment that compares three treatments during pregnancy: no diet sodas, one diet soda per day, and two diet sodas per day.
the following describes the process to randomly assign the mothers to treatments using a completely randomized design.
step 1 - write the names of all 300 mothers on identical slips of paper, put them in a hat, and mix them well.
step 2 - draw out 100 slips and assign the corresponding subjects to the group: no diet soda.
step 3 - draw out 100 more slips and assign the corresponding subjects to the group: one diet soda per day.
step 4 - the remaining 150 subjects are assigned to the group: two diet sodas per day.
step 5 - at the end of the study, weigh their 1 year old children and compare the proportion of overweight children in each group.
which step has a mistake?
○ 1
○ 2
○ 3
○ 4
○ 5

Explanation:

In a completely randomized design with three treatments (no diet soda, one diet soda per day, two diet sodas per day) and 300 subjects, the number of subjects in each group should be equal (since 300 ÷ 3 = 100). After Step 2 (100 assigned to no diet soda) and Step 3 (100 assigned to one diet soda per day), the remaining number of subjects should be 300 - 100 - 100 = 100, not 150. So Step 4 has a mistake as it incorrectly states the remaining subjects are 150.

Answer:

4