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In: Statistics and Probability

2. A sample of 25 items yields X(This is X with bar ¯ on top) =...

2. A sample of 25 items yields X(This is X with bar ¯ on top) = 60 grams and s = 5 grams. Assuming a normal parent distribution, construct a 99 percent confidence interval for the population mean weight.

3. Of a random sample of 600 trucks at a bridge, 120 had bad signal lights. Construct a 90 percent confidence interval for the percentage of trucks that had bad signal lights.

4.A cable TV company wants to estimate the percentage of cable boxes in use during an evening hour. An approximation based on previous surveys is 25 percent. The company wants the new estimate to be at the 90 percent confidence level and within 3 percent of the actual proportion. What sample size is needed?

5. Suppose that 55 percent of the voters in a particular region support a candidate. Find the probability that a sample of 900 voters would yield a sample proportion in favor of the candidate within 2 percentage points of the actual proportion.

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orchestra answered 2 years ago
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