Question

Emma is planning an experiment to examine whether reading to children increases their vocabulary size. She recruits two pre-school classes of 18-month-olds.
She assigns one of the classes to be read to three times a week for three months and the other classroom to play board games three times a week for three months.
She then measures and compares the vocabulary size of both groups.

What threat to internal validity should she be most concerned about?

Answer 1

The age of the child