A researcher is examining the relationship between the number of hours slept and score on a cognitive test, which method should be used to measure the linear relationship between these two variables?

a. Correlation

b. Proportion

c. Quartile

d. Standard deviation

A

Explanation:

Correlation shows the association between two variables for example x and y. A positive correlation means as x increases or decreases y equally increases or decreases while a negative correlation means as x increases, y decreases vice versa with correlation coefficient r between - 1 ≤ r ≤ 1. Correlation with coefficient zero shows not relation with the two variables. As r approaches 1 the correlation approaches perfect positive correlation while as r approaches - 1 the correlation approaches perfect negative correlation.

Correlation only show association but not tell whether x causes y or the situation is cause by some unseen third factor.