1. ## stats homework

A car manufacturer takes an average of 17.5 hours to construct a car. This includes time for stamping, welding, painting, assembly and inspections. Construction times vary with a standard deviation of 30 minutes and these times follow a normal distribution

b. What is the probability that a randomly selected car manufactured at this plant takes between 18 and 19 hours to construct?

c. Find the probability that the construction time for a randomly selected car manufactured at this plant is less than 17 hours and 50 minutes.

I dont think my working is correct for b. can someone help me out please

crap my photos are terrible

b is basically 1080-1050/30 to get a z-score of 1 which is 0.8413
1140-1050/30 to get a z-score of 3 which is 9.9987
Im not sure where to go from there

2. ## Re: stats homework

The answer to (b) is the area under the n(0, 1) curve between z = (18-17.5)/0.5 = 1 and z = (19-17.5)/0.5 = 3.

The answer to (c) is the area under the n(0, 1) curve between z = –∞ and z = (17.8333-17.5)/0.5 = 0.6667.

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