Suppose a team of dermatologists are testing the effectiveness of a new skin cre

Question

Suppose a team of dermatologists are testing the effectiveness of a new skin cream designed to treat rashes, but which they suspect may also make rashes worse In some patients. They run an experiment using patients with skin rashes, In which some are given the cream and some are not. For each patient, they record whether the patient's rash got better or worse. The results are in the table below. Conduct a chi-square test for independence at alpha = 0.05, using the following null and alternative hypothesis pair: H_0: whether or not a patient received skin cream and whether or not that patient's rash got better arc independent. H_a: whether or not a patient received skin cream and whether or not that patient's rash got better are dependent. a. The chi-square test statistic is: () b. The p-value for this test is: (round your answer to four decimal places) c. Based on these results, the statistical decision is: Reject H_0 and conclude that whether or not a patient received skin cream and whether or not that patient's rash got better are dependent. Fall to reject H_0 conclude that whether or not a patient received skin cream and whether or not that patient's rash got better are Independent. Reject H_0 and conclude that whether or not a patient received skin cream and whether or not that patient's rash got better are independent. Fail to reject H_0 and conclude that whether or not a patient received skin cream and whether or not that patient's rash got better are dependent.

Explanation / Answer

test statisitc=2.235

for above p value =0.1349

c) Fail to reject Howaeath or not..............are independent

Observed O Rash got better Rash got worse Total did not receive 105 23 128 received 224 73 297 Total 329 96 425 Expected E=rowtotal*column total/grand total Rash got better Rash got worse Total did not receive 99.087 28.913 128 received 229.913 67.087 297 Total 329 96 425 chi square =(O-E)^2/E Rash got better Rash got worse Total did not receive 0.353 1.209 1.562 received 0.152 0.521 0.673 Total 0.505 1.730 2.2353

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