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anonymous
 one year ago
The life expectancy of a typical lightbulb is normally distributed with a mean of 2,000 hours and a standard deviation of 27 hours. What is the probability that a lightbulb will last between 1,975 and 2,050 hours?
I figure that since one standard deviation is 27, we are looking at 3 standard deviations away from the mean(1 less than the mean and 2 more than the mean). Is this right? Where do I go from here?
anonymous
 one year ago
The life expectancy of a typical lightbulb is normally distributed with a mean of 2,000 hours and a standard deviation of 27 hours. What is the probability that a lightbulb will last between 1,975 and 2,050 hours? I figure that since one standard deviation is 27, we are looking at 3 standard deviations away from the mean(1 less than the mean and 2 more than the mean). Is this right? Where do I go from here?

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anonymous
 one year ago
Best ResponseYou've already chosen the best response.0The answer options are as follows: A 0.17619 B 0.32381 C 0.79165 D 0.96784

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0I have no idea how to do this, will fan and medal

MrNood
 one year ago
Best ResponseYou've already chosen the best response.1no  it's not 3sd from the mean it's from 1 to +2sd from mean dw:1433548569142:dw So you know tharea between mean and 1 you know th earea between mean and +2 so add them up (use 68, 95, 99.7 rule)

MrNood
 one year ago
Best ResponseYou've already chosen the best response.1(however  the answers are more accurate than the approximations you have used  so choose the answer nearest to your approximation

IrishBoy123
 one year ago
Best ResponseYou've already chosen the best response.1first you need to calc the z scores/ ie normalise. you want: \( z_{lower} = \frac{1,975  \mu}{\sigma}; \ z_{upper} = \frac{2,050 \mu}{\sigma}\) \( \mu = 2,000; \ \sigma = 27\) then you need to look \( z_{lower}\) and \( z_{upper}\) up in your tables. or on your calculator/ spread sheet. or here is a fun visual interactive: https://www.mathsisfun.com/data/standardnormaldistributiontable.html
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