
Chapter 14
508
values of Σx, Σy, Σx
2
, and Σxy must be determined. Sales is a dependent variable and advertise-
ment is an independent variable.
Computation of Σ
x
, Σ
y
, Σ
x
2
, and Σ
xy
for Example 14.1
Months Advertisement
(in thousand rupees): x
Sales
(in thousand rupees): y
x
2
xy
Jan 92 930 8464 85,560
Feb 94 900 8836 84,600
Mar 97 1020 9409 98,940
Apr 98 990 9604 97,020
May 100 1100 10,000 110,000
Jun 102 1050 10,404 107,100
Jul 104 1150 10,816 119,600
Aug 105 1120 11,025 117,600
Sep 105 1130 11,025 118,650
Oct 107 1200 11,449 128,400
Nov 107 1250 11,449 133,750
Dec 110 1220 12,100 134,200
Σx = 1221 Σy = 13,060 Σx
2
= 124,581 Σxy = 1,335,420
SS xy
xy
xy
=−
=−
×
=