Emma is planning an experiment to examine whether reading to children increases their vocabulary size. She plans to measure the vocabulary size of a group of 18-month-olds, read to them three times a week for three months, then measure their vocabulary size again. When she compares the average vocabulary at the two times, she finds that there was a significant increase in their vocabulary. Why can't she conclude that this is due to the reading?a. mortality/attrition effect. b. selection effect. c. history effect. d. maturation effect.

Maturation effect

Explanation:

Maturation is a factor that threatens the internal validity. The experiment does not happen overnight. The experiment can be happened in a couple of days, weeks, year and so on.

The dissertation experiment does not run for a long time. Many of the maturation effects occur within a very short period. It can occur within a few days. Many factors occur with subjects such as tiredness, boredom, and hunger inattention, etc.  

Thus Emma finds that there was a significant increase in their vocabulary. She does not conclude that it happened because of the maturation effect.

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explanation:

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