[Instructor] Dear students.
Today, we are going to go over practice problem 13
from Chapter 3.
First, I will read the problem
so we can understand what information is given to us.
Then, we will determine how to answer the question.
Problem 13 states a randomized control trial
was conducted to evaluate the effect of hydroxychloroquine
as a potential therapy
to prevent COVID-19 infection following exposure.
Exposed participants were randomized
to receive hydroxychloroquine or usual care
and the primary outcome was COVID-19 infection.
The investigators also assessed
the adverse event in each group
and found that 56.1% of the patients
in the hydroxychloroquine group
experienced adverse events
as compared to 5.9% in the usual care group.
So the problem is right now asking us
to calculate the relative risk of adverse event.
To answer this question,
first, we need to calculate the relative risk,
and for that, we have to use the formula.
Again, relative risk is abbreviated as RR.
Here,
the numerator is PP exposed,
and PP is our point prevalence,
and the denominator is point prevalence unexposed.
So what is our exposure here?
Our exposure is hydroxychloroquine.
And PP, again, is our point prevalence.
And our secondary outcome here is the adverse event.
So now as we try to calculate the RR,
we have to insert the proper information
that were provided to us.
So the point prevalence exposed will be 56.1%
and the point prevalence unexposed will be 5.9%.
So the answer here will be 9.5,
our c.
Now, what does this mean?
Anytime our relative risk is different from one
means that there is a dissimilarity between the groups.
So here, the group treated with hydroxychloroquine
is 9.5 times more likely
to suffer from adverse events
compared to the group that received usual care.