Dichotomization

Dichotomization

________ limits the ability to interpret differences within the data and may subjectively group results invalidly.

Note

I remind you of the statement in the syllabus and that we reviewed on day 1 regarding inclusivity and psychological research

Although not required reading today, heres a reference that discusses assessment of gender and respecting gender diversity in psychological research

Cameron & Stinson (2019)

Quantitative Variables

any variables where the data represent amounts

Dichotomization

an item or score that initially had a set of continuous values but was then separated into two possible values

It is more likely to increase following dichotomization if the results are broadly put together Note

understanding 3.b.i

Effect size

• generally, what happens to effect size following dichotomization

Power

• generally, what happens to power following dichotomization

NOTE

Anecdotally, I still see examples of this quite often)

Dichotomization limits the ability to interpret differences within the data and may subjectively group results invalidly.

What are the key problems with dichotomization?

More likely to increase correlation.

Does dichotomization increase or decrease (or both) obtained correlation?

Decrease

Does dichotomization increase or decrease (or both) effect size?

Increases in groups, decreases in correlation

Does dichotomization increase or decrease (or both) power?

It was used before, it simplified analysis, gained capability of examining moderator effects, categorized because of skewed data, using significant cutpoints, and improved statistical power.

How do researchers justify dichotomization?

When using broad age ranges, or other categorical groups that are similar for the content being tested.

When is it appropriate to dichotomize data?