Question

What level of line maintenance expense would be expected for a phone company 75,000 customer according to quadratic equation estimated regression function? Show how you arrived at this value.

	Customers (in 1000s), X	Line Maintenance Expense (in $1000s), Y	X^2	Y^2	XY
	25.3	484.6	640.09	234837.16	12260.38
	36.4	672.3	1324.96	451987.29	24471.72
	37.9	839.4	1436.41	704592.36	31813.26
	45.9	694.9	2106.81	482886.01	31895.91
	53.4	836.4	2851.56	699564.96	44663.76
	66.8	681.9	4462.24	464987.61	45550.92
	78.4	1037	6146.56	1075369	81300.8
	82.6	1095.6	6822.76	1200339.36	90496.56
	93.8	1563.1	8798.44	2443281.61	146618.78
	97.5	1377.9	9506.25	1898608.41	134345.25
	105.7	1711.7	11172.49	2929916.89	180926.69
	124.3	2138.6	15450.49	4573609.96	265827.98
Total	848	13133.4	70719.06	17159980.62	1090172.01

Answer 1

#	Customers (in 1000s), X	Line Maintenance Expense (in $1000s), Y	X^2	Y^2	XY
1	25.3	484.6	640.09	234837.2	12260.38
2	36.4	672.3	1324.96	451987.3	24471.72
3	37.9	839.4	1436.41	704592.4	31813.26
4	45.9	694.9	2106.81	482886	31895.91
5	53.4	836.4	2851.56	699565	44663.76
6	66.8	681.9	4462.24	464987.6	45550.92
7	78.4	1037	6146.56	1075369	81300.8
8	82.6	1095.6	6822.76	1200339	90496.56
9	93.8	1563.1	8798.44	2443282	146618.8
10	97.5	1377.9	9506.25	1898608	134345.3
11	105.7	1711.7	11172.49	2929917	180926.7
12	124.3	2138.6	15450.49	4573610	265828
Total	848	13133.4	70719.06	17159981	1090172
Slope:	?=(n?(xy)??x?y)/(n?x2?(?x)2)
Offset:	?=(?y???x)/n
regression equation :		y=?x+?
?	15.02
?	33.32
regression equation: Line Maintenance Expense = 15.02*Customers+33.32
Customers	75	(in 000's)
Line Maintenance Expense (in $1000s)	$          1,159.52
total level of line maintenance expense=	$ 1,159,519.26

Formulae used: