Thursday

December 18, 2014

December 18, 2014

Posted by **abby** on Tuesday, April 13, 2010 at 11:20am.

- statistics -
**drwls**, Tuesday, April 13, 2010 at 12:22pmHere is what they mean by that rule:

68% finish within one std. deviation.

95% finish within two std. deviations (50 to 90 minutes in this case).

99.7% finish withing three std. deviations.

Considering the second group, half (47.5%) will finish within 70 to 90 minutes. Since the fraction above the mean is 50% for a normal distribution, that means 2.5% will not finish at all in 90 minutes.

A more exact value, using a calculator, is 2.3%

**Answer this Question**

**Related Questions**

college statistics - the average length of time required for students to ...

DBU - The mean time to complete a psychology exam is 34 minutes with a standard ...

statistics - The times taken to complete a statistics test by all students are ...

statistics - The times taken to complete a statistics test by all students are ...

statistics - historically, the mean timr to complete this statistics test is 54 ...

statistics - Suppose the amount of time it takes for statistics students to ...

Prob ans stat - Let x be a random variable that represents the length of time it...

Math - The mean time to complete a certain stat quiz is 25 minutes, with a ...

statistics - a study of the time spent shopping in a supermarket for a market ...

statistics - A study of the time spent shopping in a supermarket for a market ...