Question

Following is an extract from the database of a construction company. The table shows the height of walls in feet and the cost of raising them. The estimated simple linear regression equation is given as Ŷ = b0 + b1X. (Hint: Use Excel functions).

Height (ft)	Cost ($)
4	670
3	430
7	810
9	1100
6	790
8	880
5	760
11	1200

4) What is the value of the coefficient b1?

A) 254.8371

B) 0.010697

C) -2.14625

D) 86.81704

5) What is the estimated cost of raising a 10 foot wall?

A) 1123.008

B) 1505.786

C) 1103.578

D) 968.6109

Answer 1

Solution :

X	Y	XY	X^2	Y^2
4	670	2680	16	448900
3	430	1290	9	184900
7	810	5670	49	656100
9	1100	9900	81	1210000
6	790	4740	36	624100
8	880	7040	64	774400
5	760	3800	25	577600
11	1200	13200	121	1440000

n	8
sum(XY)	48320.00
sum(X)	53.00
sum(Y)	6640.00
sum(X^2)	401.00
sum(Y^2)	5916000.00
Numerator	34640.00
Denominator	35946.09
r	0.9637
r square	0.9287
Xbar(mean)	6.6250
Ybar(mean)	830.0000
SD(X)	2.1148
SD(Y)	203.3060
b	86.8170
a	254.8371

4)

b1 = 86.81704

5)

estimated cost = 254.8371 + 86.81704 * 10 = 1123.008