Page 293 - Statistics for Dummies

Chapter 17: Experiments: Medical Breakthroughs or Misleading Results?
Generalizing results to people beyond the scope of the study
You can make conclusions only about the population that’s represented
by your sample. If you sample men only, you can’t make conclusions about
women. If you sample healthy young people, you can’t make your conclu-
sions about everyone. But many researchers try to do just that, and it can
give misleading results.
Here’s how you can determine whether a researcher’s conclusions measure up
(Chapter 16 has more on samples and populations):

1. Find out what the target population is (that is, the group that the
researcher wants to make conclusions about).
2. Find out how the sample was selected and see whether the sample is

representative of that target population (and not some more narrowly
defined population).
3. Check the conclusions made by the researchers and make sure they’re

not trying to apply their results to a broader population than they 277
actually studied.
Making Informed Decisions
Just because someone says they conducted a “scientific study” or a “scientific
experiment” doesn’t mean it was done right or that the results are credible
(not that I’m saying you should discount everything that you see and hear).
Unfortunately, I’ve come across a lot of bad experiments in my days as a sta-
tistical consultant. The worst part is that if an experiment was done poorly,
you can’t do anything about it after the fact except ignore the results — and
that’s exactly what you need to do.
Here are some tips that help you make an informed decision about whether
to believe the results of an experiment, especially one whose results are very
important to you:
✓ When you first hear or see the result, grab a pencil and write down as
much as you can about what you heard or read, where you heard or
read it, who did the research, and what the main results were. (I keep
pencil and paper in my TV room and in my purse just for this purpose.)
✓ Follow up on your sources until you find the person who did the origi-
nal research and then ask them for a copy of the report or paper.

3/25/11 8:13 PM
25_9780470911082-ch17.indd 277 3/25/11 8:13 PM
25_9780470911082-ch17.indd 277