A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, and distribution approximated by a normal curve. Find the percentage of bulbs that can be expected to last the period of time. Less than 690 hours

A. 97.06%

B. 47.14%

C. 97.1%

D. 97.2%

Question

A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, and distribution approximated by a normal curve. Find the percentage of bulbs that can be expected to last the period of time.	Less than 690 hours

A. 97.06%	

B. 47.14%	

C. 97.1%	

D. 97.2%

anonymous · Answer

http://www.algebra.com/algebra/homework/Probability-and-statistics/Probability-and-statistics.faq.question.252139.html

amistre64 · Answer

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amistre64 · Answer

690-500 is the distance we are from the mean

190 ; we want to measure this against the standard rule of the deviation; so divide this bu the standard deviation

190/100 = 1.9

this value is called a zscore, or a standard score and tells us how many standard deviations we are from the mean

amistre64 · Answer

we look this number up on a ztable;  .... plit it into left and right parts tho:

1.90 = 1.9  and .00|dw:1333483648431:dw|