The Root Mean Squared Error is best described as a measure of what?
Correct. As the name implies, the root mean squared error is a measure of the "average" prediction error for all points in the sample. Average is in quotes because it is in fact, a measure of the variability or dispersion of prediction errors, but it is commonly interpreted as a average.
correct answerThe "average" amount of error expected in predictions
The number of cases that have a non-zero residual
The strength of the correlation between X and Y
The sum of prediction error for all points in the sample
The sum of residuals for all points in the sample

Calculate standard error of mean and make an inference about the accuracy of the mean by analyzing problem 4.164 in Statistics for Business and Economics.

2.164 Suppose a random sample of n = 25 measurements is selected from a population with mean μ and standard deviation σ. For each of the following values of μ and σ, give the values of μx¯ and σx¯.
a. μ = 10, σ = 3
b. μ = 100, σ = 25
c. μ = 20, σ = 40
d. μ = 10, σ = 100

3. Calculate the variance and standard deviation for samples with the following statistics
Round to the nearest thousandth. I need answers for B and C.

n=11, ∑x²=87, ∑x=22 
Answer: Variance: 4.300
Standard Deviation: 2.074

b. n=41, ∑x²=367, ∑x=90
c. n=20, ∑x²=16, ∑x=15