Important Testing Considerations

When running tests of any kind, scientists must try to limit the variation between different sample groups to the independent variable(s) they are hoping to test. In psychology, this is especially difficult because even the slightest differences in environment can affect results. Furthermore, inevitable differences in preferences, interests, and general mental processes between individuals bring yet another challenge.

So, what do psychologists do to ensure their tests are as controlled as possible? There are some things nearly all experiments take into consideration.

Sex:

Scientists often like to split their sample groups randomly, but with roughly equal proportions of the male to female sexes in each group. If they do not, they may consider this in their statistical calculations when analyzing their data. For the most part, gender does not have an influence on results. However, it is worthwhile to consider that the male and female brains are different in several ways. For example, males tend to be better at spatial processing and focusing on a single task while females tend to be better at communication, empathy, and multitasking. Read more here.

Age:

Age is also an important factor in psychology simply due to the way our brains change as we grow older. Scientists have theorized that cognitive decline may begin as early as our 20s or 30s! Read more here. When their experiments do not have to do with differences in age groups, psychologists try to test a single age group. For example, many studies use college students as test subjects. 

Sample Size:

Researchers must balance having a sample size large enough to obtain accurate results from with one that is manageable considering time and resource restraints. Published studies usually use anywhere from about thirty to several hundred subjects per group. 

Other Things to Control:

The simple answer? Everything you can. 

If researchers are interacting with subjects, what they say to each sample group should ideally be scripted. Psychologists should take into consideration the color of the rooms they use, whether they test subjects individually or in groups, any background noise, the time of day, even the smell of a room or their own moods. In fact, many researchers use volunteers who aren't aware of what their research is to conduct the testing and input the data. 

In my research, I will try to keep the sample size, the proportion of males and females, the room, the scripting, the age of participants, and the time of day constant.