Question

In a study of 225 adults, the mean heart rate was 72 beats per minute. Assume the population of heart rates is known to be approximately normal with a standard deviation of 10 beats per minute. What is the 90% confidence interval for the mean beats per minute?


A. 70.7 − 73.3

B. 70.9 − 73.1

C. 70.7 − 73.1

D. 70.9 − 73.3

Answer 1

I know the answer is NOT 'D.' So which one is it and why?

Answer 2

@.Mehek. Hey, could you possibly help me out with this problem?

Answer 3

@Vocaloid Hey, just one more explanation?

Answer 4

So we're trying to come up with a ballpark estimate of the "true mean adult heart rate," based upon sampling 225 adults. In other words, we want a 90% confidence interval; we can't say for certain that the true mean adult heart rate is so and so, but can state with 90% confidence that if we took repeated samples of size 225, our confidence interval would contain this true mean 90% of the time. Hope this makes sense.

Answer 5

Makes sense. But how would we work this problem to get one of the answer choices above?

Answer 6

uhm... nvrm lol i'll just tell you the answer is 70.9-73.1

Answer 7

I honestly don't even know >.<

Answer 8

Oh Ok! Haha do you know how to get that answer though?

Answer 9

Haha never mind, I found it :D

http://openstudy.com/updates/53f977b5e4b0010fcd9819c0

Answer 10

ok lol