Question

Fred and Ted are interested in the average height of NC State students. They randomly sample students from NC State and construct confidence intervals from their data. Fred sampled 121 students to construct his confidence interval. Ted sampled 144 students to construct his confidence interval; both create histograms for their data which have symmetric, unimodal, and roughly bell-shaped distributions. Which of the following is true about the margins of error for these experiments?
a. Fred's margin of error is larger than Ted's.
b. Ted's margin of error is larger than Fred's.
c. Fred and Ted have the same size margins of error.
d. We are unable to determine which margin of error is larger without knowing more about Fred and Ted's samples.

Answer 1

Answer:

a. Fred's margin of error is larger than Ted's.

Step-by-step explanation:

Margin of error of a confidence interval:

$M = z\frac{\sigma}{\sqrt{n}}$

In which z is related to the confidence level(the higher the confidence level the larger the value of z) $\sigma$ is the standard deviation of the population and n is the size of the sample.

From this, we have that:

A higher confidence level leads to a larger margin of error.

A larger sample size leads to a smaller margin of error.

In this question:

Same confidence level.

Fred's sample is smaller, so his margin of error will be larger.

The correct answer is given by option a.