Question

the weight of a chair in a chair store   

is distributed normally

(A) The variance of those chair weights is 144 (sq. pounds).

19.5 % of all chairs are HEAVIER than 73 pounds.   

Determine the avg weight of a chair.

(B) Please determine the probability that a randomly selected

chair weighs between 49 pounds and 58 pounds?

(C)Those 5.8% of chairs which have the least weight,

all weigh less than x pounds?

(D) Z score for the chair which weighs 78.9

pounds. ?

Answer 1

Let Y be the weight of a chair in a chair store

So Y follows the normal distribution with mean = (not known)

and standard deviation =

A) We have

P(Y>73) = 0.195

So

But from normal distribution table

P(Z>0.86) =0.195

So

So

B) P(49<Y<58)

=0.3483 - 0.1271

=0.2212

C) P(Y<x) = 0.058

So

But from normal distribution table

P(Z<-1.57)=0.058

So

So x= 43.84

(D) Z score for the chair which weighs 78.9

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