A researcher used a pretest-posttest, control group quasi-experimental design. The experimental group had a mean achievement test score of 40 on the pretest and 70 on the posttest. The control group had a mean achievement score of 50 on the pretest and 60 on the posttest. What statistical technique should the researcher use to analyze these data?
a. t-test c. ANCOVA (analysis of covariance)
b. ANOVA (analysis of variance) d. chi-square
Question 2
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. The external validity question in this study would be:
a. is vocabulary instruction worth the time it involves?
b. was vocabulary instruction really responsible for the observed difference in reading scores?
c. would vocabulary instruction improve reading scores for all third graders?
d. should the teacher have exposed all the students to vocabulary instruction?
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