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Old 05-05-2015
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Post HELP- STEP 1 Behavioral Science Question

Hello, I am unable to solve these Kaplan BS Questions:

1. Why is that the answer? The question and answer are attached to this thread.

2. Why is that the answer? The question and answer are attached to this thread.

I am unable to understand both questions, even when the answer is available. I ned further explanation Please.

Thank you!
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HELP- STEP 1 Behavioral Science Question-screen-shot-2015-05-05-2.46.23-pm.png   HELP- STEP 1 Behavioral Science Question-screen-shot-2015-05-05-2.53.16-pm.png  
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Old 05-05-2015
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Quote:
Originally Posted by sm698715 View Post
Hello, I am unable to solve these Kaplan BS Questions:

1. Why is that the answer? The question and answer are attached to this thread.

2. Why is that the answer? The question and answer are attached to this thread.

I am unable to understand both questions, even when the answer is available. I ned further explanation Please.

Thank you!

1. Either this is a typo or you did not include part of the stem or explanation. 28/1000 people get a disease over a given time period (ie. 2 years), the incidence is 2.8%.

2. This is a little trickier. Looks like this was going after incidence rate, commonly reported as "person years" in epidemiology papers. This is a handy measurement. In the above example, the incidence rate is 14 cases per 1000 person years or 1.4% per year. This is handy because I can take this to mean if I observe 1000 people for a year, 14 of them will get the disease. If I observe 100 people for 10 years, 14 of them will get the disease.

In your example, they use months instead of years but the idea is the same: cases/person-at-risk-months. I think they get confusing because they take an average of persons at risk per month, and then they multiply THAT number by the two months. They should have used a different number of months to avoid the confusion.

As it is:

100 people at risk at the start
75 still at risk at the end of two months

I want to find the average of these two numbers, so (100+75)/2 = 87.5 people at risk over the time period(on average).

Now I multiply that x2 months = 175 person-months

Finally, take 25 cases / 175 person-months = 14.3% incidence per month

Put another way: approx. 14 cases per 100 person months.

Hope that helps! Behavioral science is where people tend to blow a lot of "Easy" points, so this is good stuff to get down cold!
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