1) A 99% confidence interval is +/- 2.575 standard deviations from the mean. So the formula for the interval is:

6.7 +/- (2.57)(7.1)

2) The CLT states that as your sample size increases, the mean of your sample will approach the true mean of the entire population. So how would that apply to #1? A 99% confidence interval gives a very wide range for your population weight gain. What do you think would happen to your confidence interval if they had more cows to weigh?

Jason L.

tutor

Okay I see why my answer was off. Yes, the formula is standard error of the mean * z-score +/- sample mean. You'd use standard error of the mean when measuring the sample from a population.

So using the correct formula, we should get:

6.7 +/- (7.1 / √39) * 2.575

[3.77, 9.62]

How did you get the interval you got? What steps did you take?

PS - A negative number would still have made sense because it would just mean the average cow's weight within the sample actually decreased instead of increased.

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04/18/17

Claire H.

Sorry I put the n as 3.9 into my calculator instead of 39. I am now getting the same interval as you. Thanks for all your time and help!

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04/20/17

Claire H.

04/18/17