Constructing Confidence Intervals

Deliverable 03 Worksheet

1. Discuss the importance of constructing confidence intervals for the population mean by answering these questions.

1. What are confidence intervals?
2. What is a point estimate?
3. What is the best point estimate for the population mean? Explain.
4. Why do we need confidence intervals?

Answer and Explanation:

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1. Using the data from the Excel workbook, construct a 95% confidence interval for the population mean. Assume that your data is normally distributed and σ is unknown. Include a statement that correctly interprets the confidence interval in context of the scenario.

Hint: Use the sample mean and sample standard deviation from Deliverable 1.

Answer and Explanation:

Enter your step-by-step answer and explanations here.

1. Using the data from the Excel workbook, construct a 99% confidence interval for the population mean. Assume that your data is normally distributed and σ is unknown. Include a statement that correctly interprets the confidence interval in context of the scenario.

Hint: Use the sample mean and sample standard deviation from Deliverable 1.

Answer and Explanation:

Enter your step-by-step answer and explanations here.

1. Compare your answers for (2) and (3).  You notice that the 99% confidence interval is wider.  What is the advantage of using a wider confidence interval? Why would you not always use the 99% confidence interval? Explain with an example.

Answer and Explanation:

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1. We want to estimate the mean salary in Minnesota. How many jobs must be randomly selected for their respective mean salaries if we want 95% confidence that the sample mean is within $126 of the population mean and σ = $1150.

Is the current sample size of 364 in the data set in our Excel workbook large enough? Explain.

Answer and Explanation:

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