Henry's grandfather gave him 200 collector coins. Each week, Henry purchases 20 collector coins to add to his collection.
2 answers:
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Answer:
Using a 90% confidence level
A. A sample size of 68 should be used.
B. A sample size of 98 should be used.
Step-by-step explanation:
I think there was a small typing mistake and the confidence level was left out. I will use a 90% confidence level.
We have that to find our level, that is the subtraction of 1 by the confidence interval divided by 2. So:
Now, we have to find z in the Ztable as such z has a pvalue of .
So it is z with a pvalue of , so
Now, find the margin of error M as such
In which is the standard deviation of the population and n is the size of the sample.
A. If we want to estimate the population mean time for previews at movie theaters with a margin of error of 72 seconds, what sample size should be used?
We have the standard deviation in minutes, so the margin of error should be in minutes.
72 seconds is 72/60 = 1.2 minutes.
So we need a sample size of n, and n is found when M = 1.2. We have that . So
Rounding up.
A sample size of 68 should be used.
B. If we want to estimate the population mean time for previews at movie theaters with a margin of error of 1 minute, what sample size should be used?
Same logic as above, just use M = 1.
Rounding up
A sample size of 98 should be used.