Mechanical measurements on supposedly identical objects usually vary. The variat

Question

Mechanical measurements on supposedly identical objects usually vary. The variation often follows a Normal distribution. The stress required to break a type of bolt varies Normally mean 75 kilopounds per square inch ks and standard deviation 8.3 ksi. Determine the percent to 4 decimal places of these bolts that will with standard a stress between 65 and 80 ksi without breaking using your T1-84? Using your TI-84. determine what stress is required to ensure that a bolt is in the top 20% without breaking?

Explanation / Answer

10.

Params of the normal dist. is given:

Mean = 75
Stdev= 8.3

P(65<X<80)
= P( (65-75)/8.3 Z< (80-75)/8.3)
= P(-1.2<Z<.6)
= .7257-.1151
=.6106

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