Question

Find the 95% confidence interval for the slope in each of the following settings. (Round your answers to three decimal places.)

(a) n = 20, ŷ = 24.5 + 1.8x, and SEb1 = 0.85 ,

(b) n = 30, ŷ = 30.6 + 2.3x, and SEb1 = 1.15 ,

(c) n = 100, ŷ = 29.7 + 2.3x, and SEb1 = 1.15 ,

Answer 1

(a)

Since it is simple linear regression so degree of freedom of t distribution is

df = n-2= 20-2 = 18

The critical value using excel function "=TINV(0.05,18)" is 2.101. The required confidence interval is

(b)

Since it is simple linear regression so degree of freedom of t distribution is

df = n-2= 30-2 = 28

The critical value using excel function "=TINV(0.05,28)" is 2.048. The required confidence interval is

(c)

Since it is simple linear regression so degree of freedom of t distribution is

df = n-2= 100-2 = 98

The critical value using excel function "=TINV(0.05,98)" is 1.984. The required confidence interval is