Question

The lifetimes of light bulbs are normally distributed with a mean of 1490 hours and a standard deviation of

Answer 1

Answer:

1) Proportion of light bulbs lasting less than 1380 hours.

P(X<1380) = 0.2317(4dp)

2)The longest lasting 5% of light bulbs last 1736.7 hours or more

3) The middle 85% of light bulbs last between 1274.1 and 1705.9 hours

4) Proportion of light bulbs lasting between 1310 hours and 1680 hours is 0.7823 (4 dp)

5) Proportion of light bulbs lasting more than 1680 hours is 0.1026(4dp)

6) The shortest lasting 10% of light bulbs last 1297.8 hours.

Explanation:

The calculations are handwritten and attached as files to this solution. Check the files below for all the workings