1. We have calculated a 95% confidence interval and would prefer for our next confidence interval to have a smaller margin of error without losing any confidence. In order to do this, we can
I. change the value to a smaller number.
II take a larger sample.
III. take a smaller sample.
A) I only
B) II only
C) III only
D) I and II
E) I and III
2. Which is true about a 98% confidence interval for a population mean based on a given sample?
I. We are 98% confident that other sample means will be in our interval.
II. There is a 98% chance that our interval contains the population mean.
III. The interval is wider than a 95% confidence interval would be.
A) None
B) I only
C) II only
D) III only
E) I and II
3. We have calculated a confidence interval based on a sample of size n=100. Now we want to get a better estimate with a margin of error that is only one-fourth as large. How large does our new sample need to be?
A) 25
B) 50
C) 200
D) 400
E) 1600
4. A certain population is bimodal. We want to estimate its mean, so we will collect a sample. Which should be true if we use a large sample rather than a small one?
I. The distribution of our sample data will be more clearly bimodal.
II. The sampling distribution of the sample means will be approximately nomial.
III. The variability of the sample means will be smaller.
A) I only
B) II only
C) HI only
D) and HI
E)I, II, and III
5. The manager of an orchard expects about 70% of his apples to exceed the weight requirement for “Grade A” designation. At least how many apples must he sample to be 90% confident of estimating the true proportion within ±4%?
A) 19
B) 23
C) 89
D) 356
E) 505
