Self-test help

pwoodruffe

New Member
Hey guys. I have two questions I need answered to finish an independent test.

1. In sampling without replacement from a population of 900, it's found that the standard error of the mean is only two-thirds as large as it would have been if the population were infinite in size. What is the approximate sample size?

2. In a simple random sample from a pop. that's approximately normally distriubuted, the following data values were collected:

68, 79, 70, 98, 74, 79, 50, 102, 92, 96

Based on this information, the confidence level would be 90% that the pop. mean is somewhere between:

a) 71.36 and 90.24 b) 69.15 and 92.45 c) 65.33 and 95.33 d) 73.36 and 88.24

I used the t-distribution table for this one. I came out with

80.8 plus/minus 1.833 * 28.43/sqrt10. My answer comes close but does not match any of the answers.

JohnM

TS Contributor
Try to re-compute your standard deviation - you should get 16.274, and that would push you toward choice A.

pwoodruffe

New Member
Hi John. I'm confused on recomputing my standard deviation. Also, how would your answer push me towards answer A? What should I do for question #1 as well? Thanks so much for your help.

JohnM

TS Contributor
On question 2, it looks like you're using 28.43 as the std dev, and it should be 16.274.

Sorry, but I passed right by question #1.

The adjustment to the standard error of the mean for finite populations is the formula:

(N - n) / (N - 1)

Set this equal to 2/3, plug in N=900, and solve for n (sample size).