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.

Between 290 hours and 540 hours

Answer 1

You must use a normal Cooking Oilulative distribution function. Your lower limit is 290, upper limit is 540, mean is 500, and standard deviation is 100.
So you can use your calculator and find
\(\text{normalcdf(290, 540, 500, 100)}\) or convert the bounds to z-scores and refer to a p-table, and then use the two-tailed test and subtract the probability of 290 from the probability of 540.

But that isn't your final answer, as it is asking the percentage of lightbulbs that are expected to last. So just multiply your probability you get by 5000.

Answer 2

\(\color{#0cbb34}{\text{Originally Posted by}}\) @justjm
You must use a normal Cooking Oilulative distribution function
\(\color{#0cbb34}{\text{End of Quote}}\)

No "cooking oil", the filter does that. You need to use a normal cumulative distribution function.

Answer 3

thanks

Answer 4

np