Answer:
112
Step-by-step explanation:
Given that in a study of the stability of IQ scores, a large group of individuals is tested once at age 18 and again at age 35.
Age 18: average score = 100, SD = 15
Age 35: average score = 100, SD = 15, r = 0.80
Let us obtain regression equation of y on x.
Let y be the scores at age 35 and x at age 18
Slope = [tex]r(s_y/s_x) = 0.8(\frac{15}{15} )=0.80[/tex]
The line passes through (100,100) being average of x and y
Hence regression line would be
[tex]y-100=0.8(x-100)\\y = 0.8x+20[/tex]
a) Here given that x =115
Hence [tex]y=0.80(115)+20\\=112[/tex]
the average score at age 35 for all the individuals who scored 115 at age 18, would be 112.
b) Prediction also would be the same 112.
