Gastric freezing was once a recommended treatment for ulcers in the upper intestine. Use of gastric freezing stopped after experiments showed it had no effect.  One randomized comparative experiment found that 28 of 82 gastric freezing patients improved, while 30 of the 78 patients in the placebo group improved.  We can test the hypothesis of “no difference” between the two groups in two ways: using the two-sample z statistic or using the chi-square statistic A. State the null hypothesis with a two-sided alternative and carry out the z test for proportions. Assume that the conditions are met, what are the test statistic and the p-value. B. Present the data in a 2X2 table and complete the chi-square test. Assume the conditions are met, what are the test statistics and p-value. C. Square the test statistic in part (a) and compare it to the test statistic in part (b.) What do you notice.

The Paleo diet allows only for foods that humans typically consumed over the last 2.5 million years, excluding those agriculture-type foods that arose during the last 10,000 years or so. Researchers randomly divided 500 volunteers into two equal-sized groups. One group spent 6 months on the Paleo diet. The other group received a pamphlet about controlling portion sizes. A randomized treatment assignment was performed, and at the beginning of the study, the average difference in weights between the two groups was about 0 pounds. After the study, the Paleo group had lost an average of 7.1 pounds with a standard deviation of 22.75 pounds while the control group had lost an average of 4.5 pounds with a standard deviation of 11.5 pounds. After failing to reject the null hypothesis support your answer with a p-value (a) P-value = _______

All other conditions being equal, does a larger sample size increase or decrease the corresponding magnitude of the z or t value of the sample test statistic?

A researcher wants to know if there is a statistically significant difference between Liberal Arts majors and other students on average number of books (other than those required by course work) read per year.  To test this research question, sample students attending a large university have been randomly selected.  Using the sample information suggested below, conduct a hypothesis test at 0.05 significance level. Sample 1 (Liberal Arts majors) Sample 2 (Other majors) = 16.2 = 13.7 s1 = 2.3 s2 = 9.0 N1 = 236 N2 = 321   - What is the critical Z-score?   - Compute the test statistic value (i.e., calculated or obtained Z-score).   -Determine if the null hypothesis is rejected AND state what it means.

What is the null hypothesis? Why do we want to reject our null hypothesis? The first step is the find the mean of our sample and compare it to the "hypothesized" mean of our null hypothesis—why do we do that? We use the results of our first step to calculate a test-statistic. Why is this important and how does it relate to the concept of z-score, which we learned a few weeks ago? What is a p-value? What role does it play in the rejection of the null hypothesis? What does it mean to reject the null hypothesis? Does that guarantee that the null hypothesis is false?

Acne is a common skin disease that affects most adolescents and can continue into adulthood. A study compared the effectiveness of three acne treatments and a placebo, all in gel form, applied twice daily for 12 weeks. The study's 517 teenage volunteers were randomly assigned to one of the four treatments. Success was assessed as clear or almost clear skin at the end of the 12 week period. The results of the study can be seen in the table below. Using the appropriate statistical test, determine if there is significant evidence that the four treatments perform differently. If so, how do they compare.

Researchers examine the association between the fluoridation of water and the prevention of tooth decay by comparing the prevalence of tooth decay in countries that have fluoridated water with the prevalence in countries that do not. Is this a randomized experiment or an observational study? Assume that tooth decay was seen to be less common in countries with fluoridated water. Could this result be due to confounding?

Opposing a random sample of size and equal 16A sample average of 185 it is observed the P value of the sample statistic is

For an ANOVA comparing three treatment conditions, what is stated by the null hypothesis (HO)? Question 1 options: There are no differences between any of the population means. At least one of the three population means is different from another mean. All three of the population means are different from each other. None of the other choices is correct.

You are conducting a study to see if the accuracy rate for fingerprint identification is significantly different from 0.23. You use a significance level of α=0.01      H0:p=0.23      H1:p≠0.23You obtain a sample of size n=228n=228 in which there are 70 successes.What is the test statistic for this sample? (Report answer accurate to three decimal places.)test statistic = What is the p-value for this sample? (Report answer accurate to four decimal places.)p-value = The p-value is... less than (or equal to) αα greater than αα This test statistic leads to a decision to... reject the null accept the null fail to reject the null As such, the final conclusion is that... The sample data support the claim that the accuracy rate for fingerprint identification is different from 0.23. There is not sufficient sample evidence to support the claim that the accuracy rate for fingerprint identification is different from 0.23.