From a study, the average heights of Grade 5, Grade 6 and Grade 7 boys are shown below:

Grade 5

100cm

Grade 6

105cm

Grade 7

115cm

The sample size was 1500 boys.

Develop a regression model that will allow you to compare the heights of the three grade levels.

I figure that my x variable is my grade level which I will denote as Grade 5 = 1. Grade 6 = 2, Grade 7 = 3.

The y variable will be the heights in cm.

But why am I given the sample size of 1500 boys? Isn't my "n" value the count of the grades which is 3? What do I do with the 1500? If I use 1500 as my "n", don't I need 1500 sample points?

Some guidance would be appreciated.

Thank you