Question

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. The student who weighs his rock 5 times uses the mean to calculate the 95% confidence interval for the rock weight (in grams). His interval is (25.2, 29.1). What does a 95% confidence interval for rock weight tell us in this case? Group of answer choices We are 95% confident that this interval includes the mean of the 5 weight measurements taken by this student. We are 95% confident that most rocks of this type weigh between 25.2 g and 29.1 g. We are 95% confident that the true weight of the rock is between 25.2 g and 29.1 g.

Answer 1

We are 95% confident that the true weight of the rock is between 25.2 g and 29.1 g.

Explanation:

Hello!

A geology student weighted a rock 5 times and estimated the average weight using a 95% CI [25.2; 29.1]gr

The confidence interval is used to estimate the value of the population mean, it gives you a range of values for it.

The 95% level of confidence of the interval indicates that if you were to construct 100 confidence intervals to estimate the population mean, you'd expect 95 of them to include the true value of the parameter.

So with a 95% confidence level, you'd expect the true average weight of the rock to be included in the interval [25.2; 29.1]gr

I hope this helps!