Asked by Amber
As online attacks persist, spending on information security software continues to rise. The table gives the forecast for the worldwide sales (in billions of dollars) of information security software through 2007 (t = 0 corresponds to 2002):
Year, t 0 1 2 3 4 5
Spending, y 6 8.9 11.9 14 15.7 16.2
i put y=2.1x+6.87 as the least squares equation but it's wrong. HELP PLEASE!
Year, t 0 1 2 3 4 5
Spending, y 6 8.9 11.9 14 15.7 16.2
i put y=2.1x+6.87 as the least squares equation but it's wrong. HELP PLEASE!
Answers
Answered by
Damon
use x for t
y = a + b x
x mean = 15/6 = 2.5
y mean = 72.7/6 = 12.12
x-x mean
-2.5 -1.5 -.5 +.5 +1.5 + 2.5
y - y mean
-6.12 -3.22 -.22 +1.88 +3.58 +4.08
(x - x mean)(y - y mean)
15.3 4.83 .11 .94 5.37 10.2
sum of those = 36.75
(x - x mean)^2
6.25 2.25 .25 .25 2.25 6.25
sum of those = 17.5
so
b = 36.75/17.5 = 2.1 agree with you
a = y mean - b x mean
= 12.12 - 2.1* 2.5 = 6.87 agree with you
y = 6.87 + 2.1 t
perhaps you used x in last line instead of t?
or
perhaps they want real years and billions
y = 10^9 (6.87 + 2.1(year-2002) )
y = a + b x
x mean = 15/6 = 2.5
y mean = 72.7/6 = 12.12
x-x mean
-2.5 -1.5 -.5 +.5 +1.5 + 2.5
y - y mean
-6.12 -3.22 -.22 +1.88 +3.58 +4.08
(x - x mean)(y - y mean)
15.3 4.83 .11 .94 5.37 10.2
sum of those = 36.75
(x - x mean)^2
6.25 2.25 .25 .25 2.25 6.25
sum of those = 17.5
so
b = 36.75/17.5 = 2.1 agree with you
a = y mean - b x mean
= 12.12 - 2.1* 2.5 = 6.87 agree with you
y = 6.87 + 2.1 t
perhaps you used x in last line instead of t?
or
perhaps they want real years and billions
y = 10^9 (6.87 + 2.1(year-2002) )
Answered by
Amber
i used x instead of t. thanks