Weight of a rock: In a geology course, students are learning to use a balance scale to accurately weigh rocks. One student plans to weigh a rock 20 times and then calculate the average of the 20 measurements to estimate her rock's true weight. A second student plans to weigh a rock 5 times and calculate the average of the 5 measurements to estimate his rock's true weight. Suppose the students construct a 95% confidence interval for the true weight of their rocks. Whose interval do you expect to be more precise (narrower)

The first student, with 20 measurements, will have the more precise interval due to the larger sample size.

Step-by-step explanation:

Margin of error of a confidence interval:

The margin of error of a confidence interval has the following format:

In which z is related to the confidence level, s to the standard deviation and n to the sample size.

The margin of error is inversely proportional to the square root of the sample size, which means that a larger sample will lead to a lower margin of error, that is, to a more precise interval.

In this question:

One student will use 5 measurements, other 20. The first student, with 20 measurements, will have the more precise interval due to the larger sample size.

step-by-step explanation: