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A randomized controlled trial was designed to compare the effectiveness of splinting versus surgery in the treatment of carpal tunnel syndrome. Results are given in the table below (based on data from 鈥淪plinting vs. Surgery in the Treatment of Carpal Tunnel Syndrome,鈥 by Gerritsen et al., Journal of the American Medical Association,Vol. 288,

No. 10). The results are based on evaluations made one year after the treatment. Using a 0.01 significance level, test the claim that success is independent of the type of treatment. What do the results suggest about treating carpal tunnel syndrome?

Successful Treatment

Unsuccessful Treatment

Splint Treatment

60

23

Surgery Treatment

67

6

Short Answer

Expert verified

Success is dependent on the type of treatment and the type of treatment (splint or surgery) would determine the success of treatment in the carpal tunnel syndrome.

Step by step solution

01

Given information

The data forthe success of treatment and type of treatment is provided.

The level of significance is 0.01.

02

Compute the expected frequencies and check the requirements

Theexpected frequency is computed as,

\(E = \frac{{\left( {row\;total} \right)\left( {column\;total} \right)}}{{\left( {grand\;total} \right)}}\)

The table for the observed values and the totals of row and column is represented as,


Successful Treatment

Unsuccessful Treatment

Row total

Splint Treatment

60

23

83

Surgery Treatment

67

6

73

Column total

127

29

156

Theexpected frequency tableis represented as,


Successful Treatment

Unsuccessful Treatment

Splint Treatment

67.571

15.429

Surgery Treatment

59.429

13.571

Here, all expected values are greater than 5.

Assuming the subjects are gathered from random selection and assigned randomly to the groups, the requirements of chi-square test is satisfied.

03

State the null and alternate hypothesis

The claim for independence of type of treatment and the success of treatment is tested using the following hypotheses:

\({H_0}:\)Success is independent of the type of treatment

\({H_1}:\)Success is dependent of the type of treatment.

04

Compute the test statistic

The value of the test statisticis computed as,

\[\begin{aligned}{c}{\chi ^2} = \sum {\frac{{{{\left( {O - E} \right)}^2}}}{E}} \\ = \frac{{{{\left( {60 - 67.571} \right)}^2}}}{{67.571}} + \frac{{{{\left( {23 - 15.429} \right)}^2}}}{{15.429}} + ... + \frac{{{{\left( {6 - 13.571} \right)}^2}}}{{13.571}}\\ = 9.750\end{aligned}\]

Therefore, the value of the test statistic is 9.750.

05

Compute the degrees of freedom

The degrees of freedomare computed as,

\(\begin{aligned}{c}\left( {r - 1} \right)\left( {c - 1} \right) = \left( {2 - 1} \right)\left( {2 - 1} \right)\\ = 1\end{aligned}\)

Therefore, the degrees of freedom are 1.

06

Compute the critical value

From chi-square distribution table, the critical value for row corresponding to 1 degrees of freedom and at 0.01 level of significance is 6.635.

Also, the p-value is obtained as 0.002.

07

State the decision

Since the critical (6.635) is less than the value of test statistic (9.750). In this case, the null hypothesis is rejected.

Therefore, the decision is to reject the null hypothesis.

08

State the conclusion

There is not enough evidencein favour of the claim that success is independent of the type of treatment.

It suggests that the choice of treatment would be essential to determine the success of the treatment in the carpal tunnel syndrome.

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Most popular questions from this chapter

Questions 6鈥10 refer to the sample data in the following table, which describes the fate of the passengers and crew aboard the Titanic when it sank on April 15, 1912. Assume that the data are a sample from a large population and we want to use a 0.05 significance level to test the claim that surviving is independent of whether the person is a man, woman, boy, or girl.


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