A study of class attendance and grades among firstyear stude

A study of class attendance and grades among first-year students at a state university showed that in general students who attended a higher percent of their classes earned higher grades.

Class attendance explained 25% of the variation in grade index among the students. What is the numerical value of the correlation between percent of classes attended and grade index?

Solution

As higher attendance mean higher grades, then the correlation is positive.

As 25% = 0.25 of the variaion is explained by this, then

r^2 = 0.25

Taking the square root (positive),

r = 0.5 [ANSWER, OPTION A]