Note Your answers to the questions below should follow the expectations for homework found here. Due date is on the Dates page.

Cushing’s Syndrome I

Cushings Syndrome

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
  1. Assess the independence assumption.
  2. Thoroughly (use all possible options) test the equal variances assumption.
  3. Thoroughly (use all possible options) test the normality assumption.
  4. 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.

  1. Test, at the 5% level, if the mean tetrahydrocortisone levels differ among patients with the different causes of Cushing’s Syndrome.
  2. 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.]
  3. 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.]