by Disinvestment Supporter

Created on: January 20, 2011

In a scientific experiment there are a number of terms that must always be accounted for. Other types of scientific projects exist, which employ observation and sometimes participation, are better termed case studies and ethnographies. A true experiment must have a few basic items which we should define up front. These are the major items that need to be prominently displayed for a science fair project.

*An hypothesis is a prediction of what will happen to X when Y is done to it. Sometimes this prediction is an extension or test of a theory, but other times it is just a practical question that needs answering.

*An independent variable is the Y, or the treatment received by the experimental group. Examples of Y include adding fertilizer to one plant and not another, giving students less homework, or using essay tests instead of multiple choice. There could be several independent variables, if you were measuring the effects of different kinds of fertilizers on different experimental groups for instance.

*A host of dependent variables always exist and must be accounted for. One or more of these variables will be measured to determine the effect of the independent variable.

*Finally, controls are needed to make sure the dependent variables being measured are only being influenced by the treatment and nothing else. For this reason, control groups are established when possible. A control group receives everything the experimental group(s) receives except for the treatment. An experiment is further controlled through random selection of group members.

Qualitative and Qualitative Measure of Variables

Measurement can be tricky. One example might be an experiment to determine whether adding extra fertilizer (above manufacturer's suggestions) helps plants grow larger or faster. We will need to measure time, and that is easy because time is standardized. We will also need to measure growth. Generally we think of growth in terms of height and weight, though gardeners also think of it as time to harvest AND maturity. This presents us with choices over the dependent variable to measure.

Height would be problematic in many circumstances. The height of a plant doesn't tell you whether it is bushy or has just a few leaves compared to the others. Weight would also be problematic, because we would have to kill part of our experimental and control group every time we measured. The time to harvest sounds better, easily managed, but it tells us nothing about the actual harvest (like

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