The manufacturer of an extended-life lightbulb claims the bulb has an average life of 13,000 hours with a standard deviation of 1,000 hours. If the distribution is normal, what is the approximate percentage of these bulbs that will last   A. between 14,000 and 15,000 hours? B. over 13,000 hours?

Glencoe Algebra 1, Student Edition, 9780079039897, 0079039898, 2018
18th Edition
ISBN:9780079039897
Author:Carter
Publisher:Carter
Chapter10: Statistics
Section10.4: Distributions Of Data
Problem 19PFA
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The manufacturer of an extended-life lightbulb claims the bulb has an average life of 13,000 hours with a standard deviation of 1,000 hours. If the distribution is normal, what is the approximate percentage of these bulbs that will last

 

A. between 14,000 and 15,000 hours?

B. over 13,000 hours?

C. over 12,000 hours?

D. between 11,000 and 15,000 hours?

E. between 8,000 and 21,000 hours?

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Hello! As you have posted more than 3 sub parts, we are answering the first 3 sub-parts.  In case you require the unanswered parts also, kindly re-post that parts separately.

Given that μ=13000, σ=1000.

A)

 The approximate percentage of these bulbs that will last  between 14,000 and 15,000 hours is,

P14000X15000=P14000-μσX-μσ15000-μσ                                      =P14000-130001000z15000-130001000                                     =P1z2                                     =Pz2-Pz1                                     =0.1359      from the excel function, =NORM.DIST(2,0,1,TRUE)-NORM.DIST(1,0,1,TRUE)                                     =0.1359*100%                                     =13.59%

 

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