Monday

July 28, 2014

July 28, 2014

Posted by **alice** on Wednesday, December 5, 2012 at 1:36pm.

My guess was: percentile = 9000 hours/400 lightbulbs = 22.5, but I'm not sure if I'm solving this right

- Math -
**alice**, Wednesday, December 5, 2012 at 1:50pmThis is from the actual problem - A consumer product testing lab tested 400 13-watt compact

fluorescent light bulbs by turning them all on at once, leaving them

on until they burned out, and recording the time-to-failure of each

bulb. The test revealed a symmetric and mound-shaped

distribution of times-to-failure with mean 7800 hours and standard

deviation 1200 hours. The number of lightbulbs that lasted between 5400 and 9000 hours were about 326 lightbulbs.

**Related Questions**

Stats - The distribution of lifetimes for a particular brand of lightbulbs has ...

Math - For a normally distributed distribution of variable x, where the mean is ...

math - a factory produces 150,000 lightbulbs per day. the manager of the factory...

Statistics: Percentile Rank - A survey of college students was conducted during ...

math - A box contains 12 lightbulbs. Find the number of ordered N samples of ...

statistics - The following frequency distribution presents a set of exam scores ...

statistics - Using measures of center and measures of variability compare the ...

probability - The lifetime of a type-A bulb is exponentially distributed with ...

statistics - A survey of college students was conducted during final exam week ...

Physics - Incandescent lightbulbs are filled with and inert gas to lengthen the...