-110 points BBUnderStat126.3.030.MI. Notes Ask Your Toaci Accrotime is a manufac

Question

-110 points BBUnderStat126.3.030.MI. Notes Ask Your Toaci Accrotime is a manufacturer of quartz crystal watches. Accrotime researchers have shown that the watches have an average life of 36 months before certain electronic components deteriorate, causing the watch to become unreliable. The standard deviation of watch lifetimes is 5 months, and the distribution of lifetimes is normal. (a) If Accrotime guarantees a full refund on any defective watch for 2 years after purchase, what percentage of total production will the company expect to replace? (Round your answer to two decimal places.) (b) If Accrotime does not want to make refunds on more than 6% of the watches it makes, how long should the guarantee period be (to the nearest month)? months 16/16 points i Previous Answers BBunder Stat 12 65.013 My Notes Ask Your Teacher Coal is carried from a mine in West Virginia to a power plant in New York in hopper cars on a long train. The automatic hopper car loader is set to put 69 tons of coal into each car. The actual weights of coal loaded into each car are normally HANNspree

Explanation / Answer

mean = 36
std. dev. = 5

a)
P(X < 24)
= P(z < (24 - 36)/5)
= P(z < -2.4)
= 0.0082

b)
For 6%, z-value = -1.5548
xbar = mean + z*sigma
xbar = 36 - 1.5548*5
xbar = 28.226

i.e. 28 months

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