Posted by **Tanya** on Tuesday, April 24, 2012 at 8:26pm.

The ages of commercial aircraft are normally distributed with a mean of 13.0 years and a standard deviation of 7.5 years what percentage of individual aircraft have ages greater than 15 years assume that a random sample of 49 aircraft is selected and the mean age of the sample is computed. What percentage of sample means have ages greater than 15 years

- statistics -
**PsyDAG**, Wednesday, April 25, 2012 at 11:07am
For the individual aircraft,

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score. Multiply by 100.

For the mean,

Z = (score-mean)/SEm

SEm = SD/√n

Use the same table.

- statistics -
**johnny gun**, Thursday, July 3, 2014 at 7:25pm
43

## Answer this Question

## Related Questions

statistics - If the ages of colleges students are normally distributed with a ...

statistics - The average age of doctors in certain hospital is 43 years old. ...

Statistics - The average age of chemical engineers is 37 years with a standard ...

Statistics - find the 90% confidence interval for the variance and standard ...

statistik - can you show me the calculation ;) The life expectancy of computer ...

fnu - The average age of doctors in a certain hospital is 50.0 years old. ...

Statistics - An admissions director wants to estimate the mean age of all ...

college - Assume that the life expectancy of U.S. males is normally distributed ...

statistics - the average number of years a person takes to complete a graduate ...

statistics - The mean of nonresidential buildings is 30 years and the standard ...