Answer:
Brand 1 Brand 2 Difference
37734 35202 2532
45299 41635 3664
36240 35500 740
32100 31950 150
37210 38015 −805
48360 47800 560
38200 37810 390
33500 33215 285
Sum of difference = 2532+ 3664+740+150 −805+ 560 +390 +285 = 7516
Mean = 
Mean = 
a) d= 939.5


=1441.21
b)SD= 1441.21
c)Calculate a 99% two-sided confidence interval on the difference in mean life.
confidence level =99%
significance level =α= 0.01
Degree of freedom = n-1 = 8-1 =7
So, 
Formula for confidence interval 
Substitute the values
confidence interval 
confidence interval
to 
Confidence interval
to 
Find the gradient:
m = y2-y1 / x2-x1
m = 6-(-4) / 0-1
m = 10 / -1
m = -10
Slope intercept form:
y = mx + c
Input the values from one of the points to find c (imputing (1,-4) to y=mx+c):
-4 = -10(1) + c
-4 = -10 + c
c = -4 + 10
c = 6
Therefore, the equation is:
y = -10x + 6