Control Group vs.
Controlled Variable
Controlled Variable
A controlled variable is one which is not
allowed to change unpredictably during
an experiment. Because they are ideally
expected to remain the same, they are
also called constant variables.
Example
An example of a constant variable could
be the voltage from a power supply. If
you are examining how electricity
affects an experimental subject, you
would keep the voltage constant, as
otherwise the energy supplied would
change as the voltage did.
Control Group
A control group is the experimental group tested
without changing the variable. For example, to
determine the effect of temperature on seed
germination, one group of seeds may be heated to a
certain temperature. The researcher will then
compare the percent of seeds in this group that
germinate and the time it takes them to germinate to
another group of seeds (the control group) that have
not been heated. All other variables, such as light and
water, will remain the same for each group.
Read more: http://www.answers.com/topic/experiment-3#ixzz1bELRgvYN
Example
In a trial of a drug or an experimental
procedure, a group matched with the
experimental group in all respects except the
factor under investigation. A control group is
an essential part of the scientific research
method because it ensures that any changes
observed in an experimental group are due
solely to the drug or experimental procedure
and not to any other factors.