# Thread: Variable of a population

1. ## Variable of a population

A variable of a population has a mean of 35 and a standard deviation of 42.

a. If the variable is normally distributed, identify the sampling distribution of the sample mean for samples of size 9.
b. Can you answer part a if the distribution of the variable under consideration is unknown?
c. Can you answer part a if the distribution of the variable underconsideration is unknown but the sample size is 36 instead of 9?

I have, for part a, the mean is 35 and standard deviation 14, but I'm not sure about parts b and c. I have only worked with normal distribution, how do you figure when distribution is unknown?

2. Originally Posted by sjenkins
A variable of a population has a mean of 35 and a standard deviation of 42.

a. If the variable is normally distributed, identify the sampling distribution of the sample mean for samples of size 9.
b. Can you answer part a if the distribution of the variable under consideration is unknown?
c. Can you answer part a if the distribution of the variable underconsideration is unknown but the sample size is 36 instead of 9?

I have, for part a, the mean is 35 and standard deviation 14, but I'm not sure about parts b and c. I have only worked with normal distribution, how do you figure when distribution is unknown?
Is there a requirement on sample size if the population is not known to be normal .....?

3. There is no requirement.

4. Originally Posted by sjenkins
There is no requirement.
I don't think you understood the point of my question.

The answer is Yes there is a requirement on sample size if the population is not known to be normal ........

5. OH, now I feel stupid

I had actually sat down and really pressed myself and got the answer which is what you you got. I read with large sample sizes that it tends to become more normal so you would definitely need a large sample size.

Thanks for your help though.