following parts of an experiment should be included in most science projects
and should be identified in the written paper. Correlations and other
atypical designs are exceptions.
independent variable is the variable that is intentionally
changed in the experiment, such as the temperature of the water in which
an effervescent tablet was dissolved.
levels of the independent variable are the different values
of the independent variable, such as using water at 10°, 20°,
30°, 40°, and 50° C. The levels of the independent variable
can also be thought of as the experimental groups that are set up.
dependent variable is the variable that responds to
the changes in the independent variable. For example, the time it takes
for the tablets to dissolve in the different temperatures of water is
the dependent variable.
control is the standard against which the researcher
compares the results from each treatment group (level) in the experiment.
For example, the control might be the room temperature water, which
is about 20° C. In many cases, there will not be a true control.
The researcher could then set one of the groups as the standard and
measure the other groups against that standard.
repeated trials are the number of times the experiment
is repeated to determine how the independent variable affected the results.
One complete experiment is one repeated trial.
For example, one tablet is dissolved in 10° water, one in 20°
water, one in 30° water, one in 40° water, and one in 50°
water so that 5 tablets total are used. This is ONE repeated trial
because it makes ONE complete experiment. If
the researcher tried dissolving a tablet seven different times in each
temperature of water, he/she would have seven repeated trials.
If 10 different plants are used for each treatment, then there are 10
are the things that are kept the same each time one of the trials in
the experiment is repeated. For example, constants could include the
amount of water used, the brand of effervescent tablet used, the type
of water used, and the fact that the water was not stirred. As many
outside factors as possible should be kept constant in an experiment
so that the researcher can be sure that any changes that occur do so
because of the independent variable.
For additional information on the Scientific Method, see the Intel ISEF
student website at http://www.sciserv.org/isef/students/scientific_method.asp
or in the SciFair Zone at http://www.sciencenewsforkids.org,
which is the online version of Science News for Kids.