Posted by **Jana** on Monday, December 20, 2010 at 2:14pm.

The average age of a vehicle registered in the U.S. is 8 years, or 96 months. If a random sample of 36 vehicles is selected, find the probability that the mean of their age is between 98 and 100 months. Assume the standard deviation for the population is 15. (sample mean)

- statistics -
**TutorCat**, Tuesday, December 21, 2010 at 2:23am
calculate the z scores:

z= (x-xbar)/(σ/sqrt(n))

where xbar=sample mean, σ=standard deviation of population, n=sample size, x=raw score (i.e. 98, 100)

now refer to the z chart:

http://www.thebeststatistics.info/sta/table_zvals.html

since you want the probability that the mean is between 98 and 100 months, I'd use the p-values on the right column (i.e. z-score to infinity) and take the difference of the p-values to get the area between 98 and 100.

## Answer This Question

## Related Questions

- statistics - The average age of a vehicle registered in the United States is 8 ...
- stat. - The average age of a vehicle registered in the United States is 8 years...
- Stats. - The average age of a vehicle registered in the United States is 8 years...
- Statistics - The average age of vehicles registered in the united states is 96 ...
- Statistics - The average age of chemical engineers is 37 years with a standard ...
- statistics - The average age of a child in kindergarden is 5 years or 60 months...
- statistics - The average age of statistics students nationwide is 22. The ...
- statistics - At a large publishing company, the mean age of proofreaders is 36.2...
- stats - 2. The average age of a child in kindergarten is 66 months. The standard...
- probability and statistics - the average age for licensed drivers in the country...

More Related Questions