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Engineers want to design seats in commercial aircraft so that they are wide enou

ID: 3134207 • Letter: E

Question

Engineers want to design seats in commercial aircraft so that they are wide enough to fit 90% of all males. (Accommodating 100% of males would require very wide seats that would be much too expensive.) Men have hip breadths that are normally distributed with a mean of 14.7 in. and a standard deviation of 1.1 in. Find P_90. That is, find the hip breadth for men that separates the smallest 90% from the largest 10%. The hip breadth for men that separates the smallest 90% from the largest 10% is P_90 = in.

Explanation / Answer

From information given, z=0.27, Xbar=14.7, s=1.1. Substitute the values in following z score equation to obtain the Xi.

z=(Xi-Xbar)/s

0.27=(Xi-14.7)/1.1

Xi=14.997~15 in.