From the formula for the standard deviation of the distribution of sample means, SD of x? = σ ⁄√n, you can see that the standard deviation of the sample mean is affected only by the population standard deviation and the sample size. 

a. As the sample size increases, how does the value of SD of x? change? Does it increase or decrease? 

b. As the population standard deviation increases, how does the value of SD of x? change? Does it increase or decrease? 

c. For what sample size is the SD of x? one-tenth the size of the population standard deviation?