Assignment 4

Note: This assignment was done using RStudio with R language. You can find the code for this assignment here.

Section A

Task 1 - Cohort Characteristics

Table 1 Cohort Characteristics:

Task 2

a) Homelessness by Sex

• Approximately 46.59% of the total sample reported being homeless.
• Among females, about 37.84% reported being homeless.
• Among males, approximately 49.30% reported being homeless.

b) Primary Substance of Abuse by Sex

• The total percentage of individuals who reported alcohol as their primary substance of abuse is approximately 39.36%.
• Among females, about 33.33% reported alcohol as their primary substance of abuse.
• Among males, around 41.23% reported alcohol as their primary substance of abuse.

Section B

Task 3 - Cohort Characteristics: Substance Abuse Post-Detox

Table 2 Cohort Characteristics: Substance Abuse Post-Detox:

Task 4

A. Plot the distributions of age by sex.

• The two-sample t-test indicated that there was no statistically significant difference in mean age between females and males in the sample.

B. Plot a histogram of 'lifetime number of hospitalizations for medical problems' and describe the distribution.

• The distribution of "Lifetime Number of Hospitalizations for Medical Problems" is positively skewed with a right tail.
• The mean number of hospitalizations is 3.1, with a high standard deviation indicating variability.

C. Plot a figure containing boxplots showing the maximum number of drinks consumed per day stratified by primary substance of abuse.

• The boxplot summary reveals insights into alcohol consumption and potential outliers.

Section C

Task 8

• Median for Group A (<= medianAllBili): 0.8
• Median for Group B (> medianAllBili): 3.5

Task 9

Table for Treatment Category

Table for Outcome Category

A. How many people died, and what percentage of those who died were in the placebo group?

• Total who died is 161.
• Percentage of those who died in the placebo group: 37.27%

B. What percentage of the treatment group received a transplant?

• Percentage of the treatment group (D-penicillamine) that received a transplant: 6.33%

Task 10

A. What is the risk ratio of having a transplant or dying in the treatment compared to the placebo group?

• Risk Ratio of having a transplant or dying in the treatment group compared to the placebo group: 0.92

B. How would you report this in words?

• The risk of having a transplant or dying in the treatment group (D-penicillamine) was 0.92 times lower compared to the placebo group.

C. What is the odds ratio of having a transplant or dying in the treatment compared to the placebo group?

• Odds Ratio of having a transplant or dying in the treatment group compared to the placebo group: 0.898

D. How would you report this in words?

• Individuals in the treatment group had approximately 0.898 times the odds of experiencing a transplant or death compared to those in the placebo group.

Task 11

A. Which stage has the most people in it?

• The stage with the most people is Stage 3.

B. What is the mean (SD) of age for each of the 4 stages?

C. Interpret the result of the ANOVA F-test that is shown in the output.

• The ANOVA F-test results show a statistically significant difference in mean age across different stages of the disease. The F-statistic is 7.227 with a p-value of 9.8e-05, indicating that there is strong evidence to reject the null hypothesis that the mean ages of individuals in all disease stages are equal.

D. Report the findings of the difference in mean age of people in stage 3 with those in stage 4.

• People in Stage 4 have a significantly higher mean age than those in Stage 3, with a mean age difference of approximately 4.803 years (95% CI: 1.746 to 7.860, p-value: 0.0003516).

References

1. Bretz, F., Hothorn, T., & Westfall, P. (2016). Multiple comparisons using R. https://doi.org/10.1201/9781420010909