Two important considerations I make sure to take into account as I design my study are exposure and outcome variables. The exposure variable is the variable that you predict will have an effect on the outcome variable, so, during your study, you will alter the exposure variable to measure what changes occur in the outcome variable.
Apply Your Design Option
Let’s use an example of a study objective that we have seen before. Say I am still interested in determining whether taking vitamins during early pregnancy can reduce nervous system defects in a developing fetus. I look at my study design options that allow me to find incidence, and I choose a randomized controlled trial.
In this scenario, I would then “expose” one group of subjects to vitamins early in pregnancy and would “expose” the other group to a placebo that had no nutritional content. The “exposure variable” in this case would be a binary variable that shows whether the subject received vitamin supplementation early in pregnancy or not.
The outcome variable, then, would be the presence of nervous system defects. Here, I would want to be very specific about what defects are included in my definition of “nervous system defects” to make sure that my study remains specific and that my results are usable and not too general. As with the exposure variable, the outcome variable is binary, since nervous system defects would either be present or not.
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