Table 4 shows a study population of 10 people. Each person was followed from Jan
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Question
Table 4 shows a study population of 10 people. Each person was followed from January through December, a full year. The filled in (red) blocks are the months when each participant in the study was ill. Note that some were ill before the study started in January. The empty (white) blocks indicate that the participant was well. All participants remained in the study the entire time, and the disease confers lifelong immunity upon recovery. One could not get the disease again.
Based on the above assumptions, answer the following questions. Please show all steps in your calculations, including numerators and denominators. Express all final answers as percentages.
What was the point prevalence of the disease at the start of the study (January 1st)? (2 points)
What was the point prevalence of the disease in December? (2 points)
What was the period prevalence of the disease during the first 6 months of the year (January through June)? (2 points)
What was the period prevalence of the disease during the last 6 months of the year? (2 points)
What was the cumulative incidence of the disease during the year (January through December)? (2 points)
What was the incidence density of the disease during the year (January through December)? (5 points)
a OExplanation / Answer
What was the point prevalence of the disease at the start of the study (January 1st)?
Answer :- At the start of the study there is only 1 red block thus only one out of 10 patients was ill at the beginning of the study. Therefore we have,
Point prevalence = 1/10 = 10%
What was the point prevalence of the disease in December?
Answer : In December there were 5 red blocks and 5 white blocks. Thus the point prevalence of the disease in december would be given by,
Point Prevalence = 5/10 = 50%
What was the period prevalence of the disease during the first 6 months of the year (January through June)?
Answer : During the period January to June there were 7 persons who were ill. Thus the period prevalence during January to June will be given by,
Period Prevalence = 7/10 = 70%
What was the period prevalence of the disease during the last 6 months of the year?
Answer : During the last 6months of the year(from July to December) there were 7 persons who were ill in this period. Thus the period prevalence would be given by,
Period Prevalence = 7/10 = 70%
What was the cumulative incidence of the disease during the year (January through December)?
Answer : Cumulative incidence is the percentage of people who acquire the disease at the beginning of the period. In this case we have only one person . Thus we have,
Cumulative incidence = 1/10 = 10%
What was the incidence density of the disease during the year (January through December)?
Answer : Incidence density is the percentage of people who acquired the disease during that period. 7 out of 10 people fall under this category. Therefore we have,
Incidence density = 8/10 = 80%
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