Page 28 - Statistics for Dummies

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Part I: Vital Statistics about Statistics
to be able to quickly examine and critique how a survey was designed and
conducted and be able to point out specific problems in a well-informed way.
The tools you need for sorting through surveys are found in Chapter 16.
Experiments
An experiment imposes one or more treatments on the participants in such
a way that clear comparisons can be made. After the treatments are applied,
the responses are recorded. For example, to study the effect of drug dosage
on blood pressure, one group may take 10 mg of the drug, and another group
may take 20 mg. Typically, a control group is also involved, in which subjects
each receive a fake treatment (a sugar pill, for example), or a standard, non-
experimental treatment (like the existing drugs given to AIDS patients.)
Good and credible experiments are designed to minimize bias, collect lots
of good data, and make appropriate comparisons (treatment group versus
control group). Some potential problems that occur with experiments include
researchers and/or subjects who know which treatment they got, factors not
controlled for in the study that affect the outcome (such as weight of the sub-
ject when studying drug dosage), or lack of a control group (leaving no base-
line to compare the results with).
But when designed correctly, an experiment can help a researcher establish
a cause-and-effect relationship if the difference in responses between the
treatment group and the control group is statistically significant (unlikely to
have occurred just by chance).
Experiments are credited with helping to create and test drugs, determining
best practices for making and preparing foods, and evaluating whether a new
treatment can cure a disease, or at least reduce its impact. Our quality of life
has certainly been improved through the use of well-designed experiments.
However, not all experiments are well-designed, and your ability to determine
which results are credible and which results are incredible (pun intended) is
critical, especially when the findings are very important to you. All the info
you need to know about experiments and how to evaluate them is found in
Chapter 17.
Collecting Quality Data
After a study has been designed, be it a survey or an experiment, the individ-
uals who will participate have to be selected, and a process must be in place
to collect the data. This phase of the process is critical to producing credible
data in the end, and this section hits the highlights.

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