# Calculating standard error and least square regression.

A doctor wanted to determine whether there is a relation between a
male's age and his HDL (so called good) cholesterol. He randomly selected 17 of his patients and determined their cholesterol.

a. Determine the least-squares regression equation from the sample
data.

b. Compute the standard error of y'

c. Compute the standard error of the slope "b" (note y' = a + bx)

d.Construct a 95% confidence interval about the slope.

e. Suppose a 42 year old man vists the doctor's office. What would be a good guess as to the HDL cholesterol of this patient?

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#### Solution Preview

...13 and a= mean(Y)-b mean(X)=44.94-45*-0.13 = 50.78

b) y' is actually the coefficient b=-0.13
Let e = Y-mean (Y)
The standard error =SQRT[e^2/(n-1)]= SQRT[1526.94/16]= ...