The manager of a fleet of automobiles is testing two brands of radial tires and

Question

The manager of a fleet of automobiles is testing two brands of radial tires and assigns one tire of each brand at random to the two rear wheels of eight cars and runs the cars until the tires wear out. The data (in kilometers) follow. Find a 99% confidence interval on the difference in the mean life.
Car Brand 1 Brand 2 1 37398 34680 2 45213 42016 3 36240 35500 4 32100 31950 5 37210 38015 6 48360 47800 7 38200 37810 8 33500 33215
(Express results to 5 significant digits.)

(a) Calculate =

(b) Calculate sD =

(c) Calculate a 99% two-sided confidence interval on the difference in mean life.
(--------------------- m ---------------------------  )

(d) Which brand would you prefer?

brand 2; no difference; brand 1

Explanation / Answer

Find d first which is x1-x2 =

then average the numbers to find dbar =867.125

then find the standard deviation of the numbers=1290.18

then go to stat>tests>T interval> inpt:stats

xbar=867.125

Sx=1290.18

n=8

c-level:99

answer:<-729.20,2463.40>

2607 3020 730 150 -805 560 390 285

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