# Project #26705 - Stats HW

"Smartest People Often Dumbest About Sunburns" is the headline of an article that appeared in a California newspaper. The article states that "those with a college degree reported a higher incidence of sunburn than those without a high school diploma--40% versus 33%." Suppose that these percentages were based on random samples of size 200 from each of the two groups of interest (college graduates and those without a high school diploma).

Is there convincing evidence that the proportion experiencing sunburn is higher for college graduates than it is for those without a high school diploma? Test the claim using the p-value method with a 0.1 significance level. (You should write out all the steps of the hypothesis test, even though you aren't asked to record all of them here.)

p-value =
(round your answer to four decimal places)

Decision:

Conclusion: At the 0.1 level, we  conclude that the true proportion experiencing a sunburn is higher for college graduates than it is for those without a high school diploma.

An eating attitudes test (EAT) was administered to both a sample of female models and a control group of females. (An EAT is often used to assess risk of an eating disorder). The samples resulted in the following summary statistics:

 Group Sample Size Sample Mean Sample Std Dev Models 30 8.5 5.5 Controls 30 11.35 6.8

Let μ1 denote the true average EAT score for models, and let μ2 denote the true average EAT score for controls. Construct a 99% confidence interval for the true difference in mean EAT scores. Use df = 50 when determining your critical value.

to
(round the endpoints of your CI to two decimal places)

What should go in the middle of the confidence interval, i.e. low < ___ < high?

Which of the following can you conclude based on your confidence interval?

A research team is interested in the effectiveness of hypnosis in reducing pain. The responses from 8 randomly selected patients before and after hypnosis are recorded in the table below (higher values indicate more pain). Construct a 90% confidence interval for the true mean difference in pain after hypnosis.

 Pre 9.5 12.3 13.5 12.3 12.0 13.4 10.4 11.9 Post 13.5 7.6 11.3 14.7 10.1 9.5 12.1 10.9 Difference

a) Fill in the missing table cells for the pain level differences. Compute the differences as 'Pre - Post'.

b) If the hypnosis treatment is effective in reducing pain, we expect the differences (pre - post) to be  .

Note: For (c), (d), and (e) use 3 decimals in your answers.

c) The point estimate for the true average effect (xd) that hypnosis has on pain perception is:

d) The point estimate for the true standard deviation (sd) of the effect that hypnosis has on pain perception is:

e) The 90% critical value is:

f) The 90% confidence interval for the true mean difference in pain level after hypnosis is:
< μd <
(round your answer to 2 decimals)

g) Based on your confidence interval in part (f), does hypnosis seem to have a significant effect on pain levels? Why or why not?

 Question Part Points Submissions Used
Cholesterol levels are measured for 38 heart attack patients (two days after their attacks) and 33 other hospital patients who did not have a heart attack. The sample of heart attack patients had a mean cholesterol level of 230.6 and standard deviation 35.5. The sample of other hospital patients had a mean cholesterol level of 214.8 and standard deviation 23.

The doctors leading the study think cholesterol levels will be higher for heart attack patients. Test the claim at the 0.025 level using the p-value method. Use heart attack patients as "Population 1" and non-heart attack patients as "Population 2."

(a) What type of test is this?

(b) What is the test statistic?
(round your answer to three decimal places)

(c) What degrees of freedom is associated with the test statistic calculated in (b)?
(you'll need to use the full df formula)

(d) What is the p-value?
(round your answer to four decimal places)

(e) What is the statistical decision?

(f) This means we  conclude that the true mean cholesterol level of heart attack patients is higher than the true mean cholesterol level of other hospital patients.

 Subject Mathematics Due By (Pacific Time) 04/04/2014 11:30 pm
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