mathematical measurements such as area, angle, conductivity, density, electrical
current, force, heat, humidity, length, light intensity, mass, pH, pressure,
salinity, temperature, time, velocity, volume, or others. Your teacher will
most likely require you to use only metric units or the International System
of Units (SI), so you will use centimeters instead of inches and liters instead of
gallons. The quantitative data you choose to record should be based on your
background research.
Be sure to have reasons that support the relationship between the independent
and dependent variables. For example, in an experiment that seeks
to determine whether powdered drinks contain different food dye concentrations,
it would not make sense to measure pH because pH is not the factor
being studied in the relationship between the variables.
Quantitative data are used primarily to measure your “effects.” There
are other ways, however, in which quantitative measurements are a part of
your experiment. First, you need to record measureable differences between
your experimental groups. For example, if your independent variable is pH,
you must record accurate measurements to ensure that the pH levels for each
experimental group are appropriately different from one another. Second,
you need to record quantitative measurements to ensure that extraneous
variables remain constant. For example, temperature is often an added influence
in an experiment and so must remain constant. Therefore, you must find
ways within the experimental design to keep temperature the same and then
plan to monitor and record this measurement periodically throughout the
experiment.
The type of data and how you collect it will depend on what type of STEM
research project you plan to do. In mathematics, physics, and population and
human genetics research, the data may already exist. You may even be able to
find reliable resources of data online. Then, it is a matter of obtaining the data
and organizing it so that an analysis correlating it to the dependent variable
can be made.