Exhibit 10

Exhibit 10.1: A third grade teacher feels that vocabulary instruction will help her children improve their reading scores.Half of her class receives vocabulary instruction, while the other half has a library period.She will compare reading scores after four months.
-Refer to Exhibit 10-1.The independent variable in this study is

A) reading scores.
B) vocabulary instruction.
C) gender.
D) the size of the sample.