In a randomized clinical trial to determine the most effective timing of adminis
ID: 3150551 • Letter: I
Question
In a randomized clinical trial to determine the most effective timing of administration of chemotherapeutic drugs to lung cancer patients, 22 patients were given four drugs simultaneously, while 19 patients were given the same four drugs sequentially. Objective response to the treatment (defined as the shrinkage of the tumor by at least 50%) was observed in 14 of the patients treated simultaneously and in 6 of the patients treated sequentially. a. Is this an observational or experimental study? b. What type of statistical test would you run to determine if these two treatments differ significantly? Be specific. c. Write the null and alternate hypotheses for the test in part (b). d. Find the test statistic for the analysis. e. What is the chi-square threshold value (from the table) for this analysis? f. What is your decision? Write your conclusion. g. Calculate the relative risk of responding to the treatment for patients treated simultaneously compared to these treated sequentially. Interpret it in the context of the problem. h. Calculate the odds ratio of responding to the treatment for patients treated simultaneously compared to these treated sequentially. Interpret it in the context of the problem.Explanation / Answer
simultaneously
Sequential
response
14
6
20
No response
8
13
21
22
19
41
a). This is an experimental study. ( intervention in the study)
b). Chi square test of independence or chi square test for comparing proportions is used.
c).
Null hypothesis: there is no difference in responses of simultaneous and Sequential treatments.
or
The two treatments not differ
Alternate hypothesis: there is a difference in responses of simultaneous and Sequential treatments.
or The two treatments differ
d).
Chi-Square Test
Observed Frequencies
Column variable
Calculations
simultaneously
Sequential
Total
fo-fe
response
14
6
20
3.2683
-3.2683
No response
8
13
21
-3.2683
3.2683
Total
22
19
41
Expected Frequencies
Column variable
0
simultaneously
Sequential
Total
(fo-fe)^2/fe
response
10.7317
9.2683
20
0.9953
1.1525
No response
11.2683
9.7317
21
0.9479
1.0976
Total
22
19
41
Calculated chi square =4.1934
e). chi square table value with 1 Df at 0.05 level =3.841
f).
Calculated chi square =4.1934 > 3.841, the table value.
The null hypothesis is rejected.
We conclude that the two treatments differ significantly
g).
Relative risk = (14/22)/ (6/19) = 2.015
A subject treated with simultaneously has 2.01 times or 201.5% the chance of positive response compared to treated Sequentially.
h).
odds ratio = (14*13/8*6) =3.79
The odds positive response of simultaneous treatment is 3.79 higher compared to Sequential treatment.
simultaneously
Sequential
response
14
6
20
No response
8
13
21
22
19
41
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