Use the Following Information for Questions

Multiple Choice

Use the following information for questions:
Scores on an English spelling test are determined for a sample of 16 5^th graders both before and after they learn some new vocabulary "tricks of the trade". In the population of difference scores it is know that students improve with an average of 3 points, with a standard deviation of 4 points, and that the distribution of the differences is approximately normal.
-What is the standard deviation of the sampling distribution of the sample mean difference in spelling scores?

A) 4
B) 0.25
C) 1
D) 0.75