For example, the common cold will get better in about 7-10 days without any treatment. A placebo treatment will allow a researcher to measure this spontaneous recovery. Sometimes placebos can have very strong effects, but no one is really sure how placebos work. Measurement Experiments need data. To get data, a researcher must measure something.
Measurements come in many different varieties.
For example, it is possible to measure time, weight, length, number of responses, height, pleasantness and brightness. A nominal scale classifies data according to a category only. For example, an experiment may examine which color people select. No assumptions are made that any color has more or less value than any other color. Colors differ qualitatively from one another, but they do not differ quantitatively.