Posted by **MARIA** on Monday, January 9, 2012 at 10:47pm.

A new extended-life light bulb has an average service life of 750 hours, with a standard deviation of 50 hours. If the service life of these light bulbs approximates a normal distribution, about what percent of the distribution will be between 600 hours and 900 hours?

- statistics -
**MathGuru**, Tuesday, January 10, 2012 at 4:27pm
Use z-scores.

Formula:

z = (x - mean)/sd

Find two z-scores, using 600 for x and also 900 for x. Mean = 750 and sd = 50.

Once you find the two z-scores, use a z-distribution table to determine your probability between the two z-scores.

## Answer This Question

## Related Questions

- Stats - A new extended-life light bulb has an average service life of 750 hours...
- statisitics - A company installs 5000 light bulbs, each with an average life of ...
- math - 1) A light bulb producing company states that its lights will last an ...
- statistics, help - Can someone help me which way can I approach this problem. A ...
- statitics - a light bulb manufacture gaurentees that the mean life of a certain ...
- Business Statistics - The quality control manager at a light bulb factory needs ...
- Statistics - An electrical firm which manufactures a certain type of bulb wants ...
- Statistics - An industrial engineer has found that the standard household light ...
- stat - A company installs 5000 light bulbs, each with an average life of 500 ...
- maths - the life span of an electric bulb is normally distribution with mean ...

More Related Questions