# Sample Mean and Population Mean: Standard Deviation

Please explain how to set up and solve. I have attempted to answer, please let me know if right or wrong...

A sample of n= 36 scores is selected form a population with o= 12. if the sample mean of M=56 produces a z score of z= +3.00 then what is the population mean?

* 56

*52 (is this correct?)

* 54

*50

A sample of n= 9 scores is obtained from a population with u= 70 and o= 18. if the sample mean is M=76, what is the z-score for the sample mean?

* z= 0.50

*z= 1.00

*z= 0.33 ( is this correct?)

* z= 3.00

A random sample of n=4 scores is obtained from a normal population with u= 30 and o= 8. what is the probability that the sample mean will be smaller than M= 22?

* 0.00003

* 0.1587 ( is this correct?)

* 0.3085

* 0.0228

a random sample of n= 9 scores is obtained from a normal population with u= 40 and o= 18. what is the probability that the sample mean will be greater than M= 43?

* 0.1587

*0.0228

*0.4325 ( is this correct?)

* 0.3085

https://brainmass.com/statistics/probability/sample-mean-and-population-mean-standard-deviation-584638

#### Solution Preview

1.

=> M-u = z*o/sqrt(n)

=> 56 - u = 3*12/sqrt(36)

=> u = 56 - 3*12/6 = 50

2.

z = ...

#### Solution Summary

A few problem related to sample and population mean are solved here.