# discussion board unit 10

The formula for calculating a 95% confidence interval for a population mean is:

The general â€œConfidence Intervalâ€ formula is:

sample mean â€“ E < population mean < sample mean + E

To calculate a confidence interval, the margin of error (E) must first be calculated.

The Margin of Error, E, for means is: E = 1.96*s/sqrt(n), where s is the sample standard deviation, n is the sample size. The â€œsqrtâ€ stands for square root.

The Margin of Error, E, for proportions is: E = 1.96*sqrt[p*(1-p)/n], where s is the sample standard deviation, n is the sample size, and p is the proportion.

- Use the Confidence Interval formula above, and the correct formula for E, to and calculate the 95% confidence interval for any population mean of your choice. Write down (invent) the sample size (be sure it is 30 or above), the sample mean, and the sample standard deviation. Then, calculate the confidence interval. Remember, you are inventing all the values, so no two posts should look the same.
- Use the Confidence Interval formula above, and the correct formula for E, to and calculate the 95% confidence interval for any population proportion of your choice. Write down (invent) the sample size (be sure it is 30 or above) and the sample proportion. Then, calculate the confidence interval. Remember, you are inventing all the values, so no two posts should look the same.

Hint: The PowerPoint Guides has great examples to learn from before creating your own unique and original example.

Please create personalized and substantive responses to at least two other student main posts. In your response, include the following:

Choose any two classmates and review their main posts.

- Review all student work for calculating a confidence interval for a sample mean. Redo their work and confirm that it is correct, or correct it and note the errors. What is the final margin of error E? What is the final confidence interval? Offer an example sample mean that would fit into the confidence interval. Offer an example sample mean that would be outside of the confidence interval.
- Review all student work for calculating a confidence interval for a sample proportion. Redo their work and confirm that it is correct, or correct it and note the errors. What is the final margin of error E? What is the final confidence interval? Offer an example sample proportion that would fit into the confidence interval. Offer an example sample proportion that would be outside of the confidence interval.

TEXTBOOKS

Bennett, J., Briggs, W.L. & Triola, M.F. (2013) Statistical Reasoning for Everyday Life (4th ed.). Upper Saddle, NJ: Pearson.