A field biologist is studying black bear cubs in Yellowstone National Park. With

Question

A field biologist is studying black bear cubs in Yellowstone National Park. With the help of park rangers, he tranquilizes 17 bear cubs and their mothers and weighs the cubs. He calculates the margin of error in estimating the true mean weight of bear cubs and gets 5.818 lbs, at 95% confidence. Which of the following would produce a smaller margin of error?

A) Weighing the cubs without tranquilizing them

B) Weighing the cubs without tranquilizing them

C) Weighing fewer cubs.

D) Using a higher confidence level

A fellow-student calculates a 99% confidence interval for a mean and gets (0.030, 0.035). He says that there is a 99% chance that the true mean is between 0.030 and 0.035. Is he right? Why or why not?

A) No. Once the confidence interval is calculated, the probability that it contains the true mean is either 1 or 0.

B) No. Something always goes wrong in any study, so the chance that the true mean is in the interval is probably less than 99%.

C)Yes. The phrase "99% confidence" means there's a 99% chance that the confidence interval contains the true mean.

D) Yes. His confidence interval is based on a random sample, so there is a 1% chance that it does not contain the true mean.

Explanation / Answer

B) Weighing the cubs with tranquilizing them as this decreases standard deviation and also margin of error.

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A) No. Once the confidence interval is calculated, the probability that it contains the true mean is either 1 or 0.

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