Stat 160 Prequiz over Section 7.1, 7.2



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1. To build a 95% confidence interval for the mean we need
the sample mean only.
the first and the third quartiles.
the standard deviation.
the sample size, the sample mean and the sample standard deviation.
2. If the 95% confidence interval for the population mean is (10,40), what is the value of the sample mean?
30.
50.
25.
Not enough information.
3. Suppose we have two sampling situations A and B. Suppose each has the sample size 10 and each has the sample mean 20. But Situation A has sample variance 40 while Situation B has sample variance 80. Which situation has the wider 95% confridence interval for the population mean?
Situation A
Situation B
Both the same.
Insufficient information
4. Suppose the 95% confidence interval for the population mean is (5,10). Which of the following is best conclusion?

The probability that the true mean is greater than 10 is .05.
We are 95% confident that the true mean lies between 5 and 10.
We are 95% confident that the sample mean is beyond 10.
We are 95% confident that the sample mean is less than 5.