For question 2.37 part a, Why are the mu and sigma parameters calculated like that?

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter10: Sequences, Series, And Probability
Section10.8: Probability
Problem 32E
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For question 2.37 part a, Why are the mu and sigma parameters calculated like that?

P(L > 10000)
Following above procedure
In T –u
Z =
In 10000-9.3790
= -1.0187
0.1655
P(Z) = 0.1538
P(L>10000) = 1 – P(L<10000) = 1 –- 0.1538 = 0.846
P(L=12000 | L>10000) = 0.468 * 1/ 0.846 = 0.55324
Transcribed Image Text:P(L > 10000) Following above procedure In T –u Z = In 10000-9.3790 = -1.0187 0.1655 P(Z) = 0.1538 P(L>10000) = 1 – P(L<10000) = 1 –- 0.1538 = 0.846 P(L=12000 | L>10000) = 0.468 * 1/ 0.846 = 0.55324
Prob 2.37 - The life of a light bulb is lognormally distributed with mean of 12,000 h and standard
deviation of 2000 h. Compute the probability that
a) A light bulb will last 12,000h
b) A light that has already worked for 10,000 h will last 12,000 h
ANS: Given
Hy = 12000, oy = 2000
He= In
= 9.379
1+0*o
O *0
Of = In
| =0.1655
Р(В> 12000)
First we have find Z values for which from the tables we get P(B<12000).
In T-H
Z =
In 12000-9.3790
= 0.0827
0.1655
P(Z=0.0827) = 0.532
P(B>12000) = 1 - P(B<12000) = 1 - 0.532 = 0.468
P(L=12000 | L>10000)
P(L=12,000)× P (L>10,000V L=12,000)
P(L>10000)
Transcribed Image Text:Prob 2.37 - The life of a light bulb is lognormally distributed with mean of 12,000 h and standard deviation of 2000 h. Compute the probability that a) A light bulb will last 12,000h b) A light that has already worked for 10,000 h will last 12,000 h ANS: Given Hy = 12000, oy = 2000 He= In = 9.379 1+0*o O *0 Of = In | =0.1655 Р(В> 12000) First we have find Z values for which from the tables we get P(B<12000). In T-H Z = In 12000-9.3790 = 0.0827 0.1655 P(Z=0.0827) = 0.532 P(B>12000) = 1 - P(B<12000) = 1 - 0.532 = 0.468 P(L=12000 | L>10000) P(L=12,000)× P (L>10,000V L=12,000) P(L>10000)
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