Reference no: EM132844124

Confidence intervals and sample size

Start by reviewing the following Handy Helpers, which are also provided in this week's Lesson: Week 5 Confidence Intervals Mean - for Price Data.pdf and Week 5 Confidence Intervals Proportions - for Proportion Data.pdf. These documents will give you step by step examples on how to use Excel to calculate confidence intervals. DO NOT do these calculations by hand. Let Excel do the heavy lifting for you.
Initial Post:

Use the data you identified in Week 1, and solve the following:

Question 1. Find the sample mean and sample standard deviation for your 10 vehicle prices (HINT: you already did this during week 2... you found the mean and standard deviation for your original 10 vehicle prices, without the super car). Next, calculate the 95% confidence interval for the population mean (NOTE: The sample size is small, therefore use the "Sigma unknown" Confidence Interval with the T distribution, rather than the Z distribution). In your post, provide your mean, standard deviation, sample size, and t-critical value so that your classmates can use your values to check your calculations and compute their own confidence intervals. Also, interpret your interval for the population mean - explain what your interval means using words.

Question 2. Find the proportion people that said Yes to the question you identify in Week 1 (HINT: you already did this during week 3). Define p^ to be the proportion of people that said Yes to your Week 1 Question. Next, calculate the 95% confidence interval for the population proportion. In your post, provide your sample proportion, p^, the sample size, and z-critical value so that your classmates can use your values to check your calculations and compute their own confidence intervals. Also, interpret your interval for the population proportion - explain what your interval means using words.
Respond to two peers:

Question 3. For this question, use answer to question 1 and Calculation #1 below. (Another CI for the Mean): Pick another confidence level, i.e. 90%, 99%, 97%, 83%, etc. Using confidence level from question 1, find the confidence interval using Calculation 1 mean vehicle price (HINT: Use the sample mean, standard deviation, and sample size) - though change the t-critical value for your new confidence level) Compare your newly calculated confidence interval for the population mean to the 95% confidence interval in question. How do they differ?

Question 4. For this question, use answer to question 2 and calculation #2 below. (Another CI for the Proportion): Pick another confidence level, i.e. 90%, 99%, 97%, 83%, etc. Using confidence level from question 2, find the confidence interval using Calculation #2 below. (HINT: Use the sample proportion, and sample size in calculation #2 - though change the z-critical value for your new confidence level) Compare your newly calculated confidence interval for the population proportion to the 95% confidence interval in question 2. How do they differ?

Question 5. Instructions: Your initial post should be at least 150 words. Also, you MUST attach your Excel file with the formulas that you used to solve the questions above. NOTE, you will have 4 total confidence intervals when you finish this post.

Attachment:- Confidence intervals.rar