Epidemiology Assignment 5

Question 1: Now, as you look through Chapter 6 in the textbook, you will recognize many of these types of charts, graphs or tables that were described in the CDC Manual. Let’s look at a few of them in more detail. 

In Figure 6-1. These two graphs are similar in that these are both both bar graphs with two variables being compared. They are both comparing frequencies during the individual years between 1978-2010. 

1. Explain how are these two graphs are different.

Questions 2-7: In Figure 6-4 these figures are comparing Risk Groups of AIDS patients  from two different years. Answer these questions;

Look in Lesson 3: Measures of Risk

 Section 1: Frequency Measures

2. Which of the following parameters is being compared in this graph? Highlight your answer. 

 a. Ratio

 b. Proportion

 c. Incidence Rate

3. Explain what the term “Cumulative” means in this analysis. 

4.  In comparing the data from 1986 to 2010, name 4 major changes that occurred in frequency among the different Risk groups.

5. Explain why the Blood Transfusion and Hemophiliac patient group appear to disappear?

6. Why does the frequency in the Homosexual group go down so dramatically? Are there fewer homosexual patients in 2010 than there were in 1986? 

7. Why did the percentage of Heterosexual patients increase between 1986 and 2010?

Questions 8-9: When we see tables and graphs, we are often too quick to jump to conclusions about what they are trying to tell us. Read the Section in the textbook on 110-111, Epidemiology and Modes of HIV Transmission and Anal Sex – A High-Rsik Mode. Now look at Table 6-2.

Let’s see if you can figure out what this Table is telling you. The frequencies (percent HIV Seropositive) do not add up to 100%. They would have, if they had been comparing the Proportion of patients who had converted to Seropositive as the result of the different types of sexual activities. By reading the text carefully, you can figure out what these percentages are actually referring to. 

8. What are the percentages in Table 6-2 referring to? Percent of what?

9. Explain the main finding of Table 6-2. 

Question 10: Sometimes we see charts that we are not familiar with. We don’t know what to think! What do most people do when confronted with a chart they don’t understand? They skip over it! Figure 6-7 is an example of this. Actually, the finding of of this chart is dramatic. It would be a shame to miss out on it because you didn’t know how to read it. 

You will find an explanation of this type of chart, also known as a pyramid chart in Lesson 4, Section 3 (scroll down to Figure 4.10 Population Distribution of Zambia by Age and Sex, 2000). Read that section, then use it to interpret the pyramid chart in Figure 6-7, on p. 119 of the textbook. 

The goal of this graph is to examine how the age distribution of the population of Lesotho, a country in southern Africa, has changed over time as a result of the AIDS epidemic. For the graphs in this figure, they are looking at a the Proportion of the population in each age group. 

Each bar represents what percentage of the population was in each age group during the year that they are plotting (age 0-5; 6-10; etc).  The total should add up to 100%. Note: This is a Proportion that they are looking at (see Lesson 3, section 1).

10. Explain why the overall shape of the pyramid changed between 1950 and 2007. What is the main finding of this pair of charts?