Exercise: Vocabulary, age, and epilepsy, 5

Question 5: All the correlations are significantly different from zero. What can we conclude about the relationships between psychological test performance and age?

Suggested answer

Because the correlations coefficients are significantly different from zero, there is good evidence that both vocabulary test score and verbal learning test score are related to age in the population.

For vocabulary, score increases with increasing age (i.e. is larger for older people, we don't know whether an individual's score increases with age). This is true both for the epileptics, whose data we can see, and for the controls, whose data we cannot see. The relationship is fairly weak in each population. It may be slightly stronger for the epileptics, because their correlation is further from zero than that for the controls, but we cannot say without further analysis whether this difference is significant.

For verbal learning, score decreases with increasing age (i.e. is smaller for older people). This is true both for the epileptics and for the controls. The relationship is fairly weak in each population. It appears to be of very similar strength in each sample.

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