# According to the stock index, the return from January 2014 to December 2014 shows the average of 7% with standard deviation of 2.5%.4)  Suppose the population mean is unknown, but we know the population standard deviation is 2.5. What is the 95% confidence interval of population mean if the sample mean is 7.2\$ and the sample standard deviation is 3% from randomly selected 25 stocks?5) Suppose the population mean and the population standard deviation are unknown. What is the 95% confidence interval of population mean if the sample mean is 7.2\$ and the sample standard deviation is 3 from randomly selected 25 stocks?

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According to the stock index, the return from January 2014 to December 2014 shows the average of 7% with standard deviation of 2.5%.

4)  Suppose the population mean is unknown, but we know the population standard deviation is 2.5. What is the 95% confidence interval of population mean if the sample mean is 7.2\$ and the sample standard deviation is 3% from randomly selected 25 stocks?

5) Suppose the population mean and the population standard deviation are unknown. What is the 95% confidence interval of population mean if the sample mean is 7.2\$ and the sample standard deviation is 3 from randomly selected 25 stocks?

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Step 1

4)

Assume that the population standard deviation is 2.5\$.

The provided information is:

Step 2

Here the population standard deviation is known so we use Z-statistic to compute the confidence interval.

The confidence interval for population means, at 95%, can be calculated as:

Step 3

5)

The provided information is:

Assume that the ...

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