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Replacement times for Maytag washer and dryer sets are normally distributed with a mean of 5.2 years
and a standard deviation of 1.1 years.
Round all final answers to 3 decimals.
(a) Find the replacement time (in years) that separates the top 17 % from the bottom 83 %.
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They want you find the z-mark on the time line under the normal curve,
which separates the lower 0.83 area (on the left) from the upper 0.17 area (on the right).
Use the standard function invNorm of the regular hand calculator TI-83/84
The format is
area on
the left mean SD
the replacement time (in years) = invNorm( 0.83, 5.2, 1.1)
The answer is P = 6.25 years for the replacement time (rounded).
Alternativaly, you may use an online (free of charge) calculator at this web-site
https://onlinestatbook.com/2/calculators/inverse_normal_dist.html
It has simple interface and shows the area of the interest under the normal curve,
so it is very good tool to learn the subject, if you are a beginner student in such statistical calculations.
Of course, the online calculator will give you the same answer as the regular hand calculator TI-83/84.
Solved.