A study used X-ray computed tomography (CT) to collect data on brain volumes for

Question

A study used X-ray computed tomography (CT) to collect data on brain volumes for a group of patients with obsessive-compulsive disorders and a control group of healthy persons Volumes of the right cordate (in milliliters) are provided in the table below Obsessive-Compulsive Grou Control Group 0.308 0.407 0.463 0.210 0.455 0.334 0.304 0.287 0.340 0.344 0.288 0.305 0.519 0.501 0.334 0.476 0.460 0.429 0.594 0.445 0.402 0.483 0.349 Use the Wilcoxon rank-sum test with a 0.01 significance level to test the claim that obsessive-compulsive patients and healthy persons have different brain volumes. Based on this result, can we conclude that obsessive-compulsive disorders have a biological basis?

Explanation / Answer

The null hypothesis will be

H0: Obsessive-compulsive patients and healthy patients have same brain volumes.

and the Alternative hypothesis will be

H1: Obsessive-compulsive patients and healthy patients have different brain volumes. Or the median of two population differs significantly.

Assumptions:

1. The two samples are independent of one another
2. The two populations have equal variance or spread

Analysis:

Wilcoxon rank sum test with continuity correction

Wilcoxon test statistic = 18.5, p-value = 0.002209

Since the p-value 0.002209 is less than the level of significance 0.01, we reject our null hypothesis and conclude that the Obsessive-compulsive patients and healthy patients have different brain volumes and we can conclude that obsessive-compulsive disorders have a biological basis.

Thank You

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