Confidence Interval Concepts

Confidence Interval Concepts

(Required) Create and post a response that fully answers one of the 10 questions below (no later than Wednesday)

(Required) Create and post a response that fully answers a different one of the 10 questions below (on a different day)

(Required) Post one quality response to another classmates’ “main” post or to a professor post (by the end of the week).

(Required) The posts must be submitted on at least 3 different days.

(Optional) Additional posts and/or days of participation are not required, but are certainly welcome!

NOTE: Always paste the question itself (and its number) above your answer (or enough of it, when it’s a really long question, to make it clear which one you are addressing).

For full posting guidelines, review the Real World Discussions: Requirements page.

1. Find a Survey or Poll… Confidence Interval

1. Look in the newspapers, magazines, or other news sources for results of a survey or poll that show the confidence interval, usually as a +/- amount.  Describe the survey or poll and then describe the interval shown.  How does knowing the interval, rather than just the main result impact your view of the results?

2. Confidence Intervals …Sample

2. Calculate the 90% and 95% confidence intervals of the following data set assuming this is sample data.  Describe your process as well as the difference in the intervals.

          5  6  3  3  4  2   7  8  9  2  5  4   3   11  21   31  22  27  28  14

3. Confidence Intervals …Population

3. Calculate the 90% and 95% confidence intervals of the following data set assuming this is population data.  Describe your process as well as the difference in the intervals.

          5  6  3  3  4  2   7  8  9  2  5  4   3   11  21   31  22  27  28  14

4. Why?

4. Why are sample and population confidence intervals calculated differently?

5. Teenagers DO Eat Pizza!

5. Say that on average teenagers eat 10 slices of pizza each week, with a 95% confidence interval of (8-12).  We take a sample of teenagers and find that this group eats an average of 6 slices each week.  What can we say about the teenagers in the sample in relation to the confidence interval?

6. Impact of Differences

6. Calculate and show the 95% confidence interval for males and females separately.  What impact are the different means having on the intervals and what impact are the different standard deviations having?

                Females:  43  48  54   55  33  48   62   68   54  61

                Males:  62  75  54  59  21  22  50  59  62  38

7. More Weekly Pizza!

7. Say that on average teenagers eat 10 slices of pizza each week, with a 95% confidence interval of (8-12).  We take a sample of teenagers and find that this group eats an average of 9 slices each week.  What can we say about the teenagers in the sample in relation to the confidence interval?

8. Minimum Sample Size

8. Describe the process of finding the minimum sample size for a given level of confidence and a given margin of error.  Describe a situation where finding the minimum sample size would be helpful.

9. Distribution Shapes

9. Describe the difference in the shape and nature of the t and z distributions.  In what ways are they the same?  Do they change in shape?  If so, what causes the change?  If not, why not?

10. Ethics! (Decisions, Decisions)

10. Ethics:  Describe a decision you might have made in the past or might make in the future where knowing a confidence interval would/could have helped you in making that decision.  How might the interval improve or detract from the decision?

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