Lesson 3 Flashcards
Observational Study
A study is considered an observational study
if researchers observe or measure specific
characteristics of their sample members, but
they do not attempt to modify or influence
these characteristics.
What makes an experiment apply a treatment ?
A study is considered an experiment if
researchers apply a treatment and then
observe its effects on the members of the
sample.
Researchers are interested in the link between smoking during pregnancy and birth weight
of babies. They gather a sample of 400 pregnant women and compare the average birth
weight of babies born to mothers who smoked during pregnancy versus those who didn’t
smoke during pregnancy. Is this an observational study or an experiment? How do we
know?
This is an observational study. Researchers are recording whether pregnant women
smoked and what weight their babies were. The researchers are not manipulating which
group someone is in (e.g. telling some pregnant women to smoke)
Example: In the clinical trials to develop a COVID-19 vaccine, researchers randomly chose
half the participants to take the potential vaccine and had half take something like salt
water in its place. They then measured the percentage of people in each group who got
COVID-19 over time.
Who is in the treatment group? Who is in the control group?
Treatment group – half receiving potential vaccine / Control group – half receiving salt
water
