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anonymous
 one year ago
the life expectancy of a typical light bulb is normally distributed with a mean of 2000 hours and a standard deviaton of 27 hours. what is the probability that a lightbulb will last between 1975 and 2050 hours?
a.)0.17619
b.)0.32381
c.)0.79165
d.)0.96784
anonymous
 one year ago
the life expectancy of a typical light bulb is normally distributed with a mean of 2000 hours and a standard deviaton of 27 hours. what is the probability that a lightbulb will last between 1975 and 2050 hours? a.)0.17619 b.)0.32381 c.)0.79165 d.)0.96784

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Vocaloid
 one year ago
Best ResponseYou've already chosen the best response.1convert 1975 and 2050 to zscores using the formula zscore = (given number  mean)/standard deviation then use a ztable or a calculator (normalcdf(zscore1,zscore2) to find the probability

Vocaloid
 one year ago
Best ResponseYou've already chosen the best response.1http://4.bp.blogspot.com/_5u1UHojRiJk/TEh9BHxxPUI/AAAAAAAAAIQ/DafeQNMYFoE/s1600/ztable.gif

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Okay.. how would I find the zscores?

Vocaloid
 one year ago
Best ResponseYou've already chosen the best response.1use the formula I just gave you

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Would the answer be 0.96784

Vocaloid
 one year ago
Best ResponseYou've already chosen the best response.1hm, not quite, can you tell me where you got your answer?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0I'm a little confused on how to do this all. The two answers I got were .925925926 and 1.851851852

Vocaloid
 one year ago
Best ResponseYou've already chosen the best response.1your numbers are right, you're just not done yet 1. find the probability that corresponds to .925925926 using the ztable 2. find the probability that corresponds to 1.851851852 using the ztable take the result from part 2 and subtract the result from part 1

Vocaloid
 one year ago
Best ResponseYou've already chosen the best response.1uh, not quite use the ztable to find the probability that corresponds to .925925926

Vocaloid
 one year ago
Best ResponseYou've already chosen the best response.1actually, do you have a graphing calculator with you?

Vocaloid
 one year ago
Best ResponseYou've already chosen the best response.1alright, so for the zscore .925925926 we're going to round to 0.93, and use this ztable to find the probability https://www.bing.com/images/search?q=negative+z+table&view=detailv2&&&id=0EE0897D340872D7DD333EA703C06E1FAFE3D682&selectedIndex=0&ccid=UAu%2f5RDN&simid=608005827397226440&thid=JN.QiHVxQ5sExJprxixifrppg&ajaxhist=0 look at the left column and find the row 0.9, then go across to the column 0.03 and tell me what number is in the box

Vocaloid
 one year ago
Best ResponseYou've already chosen the best response.1dw:1433555811431:dw

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0.1762 so it's the first answer. Thank you :)

Vocaloid
 one year ago
Best ResponseYou've already chosen the best response.1ahh sorry for the late reply you're supposed to do the same thing we just did for 1.851851852 and subtract the two values
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