Cushing’s Syndrome I
Cushing’s syndrome is a condition in which the adrenal cortex overproduces cortisol. Patients suffering from Cushing’s syndrome were divided into three groups based on the cause of the syndrome: adenoma, bilateral hyperplasia, and carcinoma. The level of tetrahydrocortisone in the urine of each patient was recorded for each individual with these causes, as shown below. Load these data into R to answer the questions below.
Adenoma: 3.1, 3.0, 1.9, 3.8, 4.1, 1.9 Bilateral hyperplasia: 8.3, 3.8, 3.9, 7.8, 9.1, 15.4, 7.7, 6.5, 5.7, 13.6 Carcinoma: 10.2, 9.2, 9.6, 53.8, 15.8
- Assess the independence assumption.
- Thoroughly (use all possible options) test the equal variances assumption.
- Thoroughly (use all possible options) test the normality assumption.
- Thoroughly (use all possible options) test the outliers assumption.
Cushing’s Syndrome II
Continue with the data from above but with the outlier removed. You must remove the outlier using R code (not by removing it from the CSV file). Do not attempt a transformation with the data and do not check the assumptions again.
- Test, at the 5% level, if the mean tetrahydrocortisone levels differ among patients with the different causes of Cushing’s Syndrome.
- If a difference in means was identified, then (using an appropriate method) determine which group means differed significantly from each other. [Notes: Provide complete tabular AND graphical support for your answer. Your graph should clearly articulate which groups differ and which do not.]
- For any differences identified above, provide an appropriate statement describing the amount of difference (use CIs) between the group means. [Notes: Refer to appropriate tabular results. Clearly identify which group had a larger mean.]