Makeup Directions: Choose the best answer.
1. Which of the following checks are NOT made when constructing a confidence interval for
the difference of two means in an observational study.
a. Both samples are random selections from the population.
b. Both Populations are at least ten times bigger than the samples.
c. Both the expected number of successes and expected number of failures are
least 10
d. Both the samples are at least 30.