Use the Following Information for Questions:
Scores on an English

Multiple Choice

Use the following information for questions:
Scores on an English spelling test are determined for a sample of n = 25 fifth graders both before and after they learn some new vocabulary "tricks of the trade". In the population of all differences in scores it is known 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 z-score if the mean difference in the sample was $\overline{d}$ = 4.5?

A) 0.625
B) 0.375
C) 1.875
D) 9.375