Answer:
The estimated impact of the experiment of offering test preparation classes is:
= 8 scores (in performance improvement).
Step-by-step explanation:
Average standardized-test score for the first 10 high schools = 69
Average standardized-test score for the second 10 high schools = 70
After 6 months:
Average standardized-test score for the first 10 high schools offered test preparation classes = 78
The change in the average standardized-test score for the first 10 high schools = 9 (78 - 69)
Average standardized-test score for the second 10 high schools not offered test preparation classes = 71
The change in the average standardized-test score for the second 10 high schools not offered the prep = 1 (71 - 70)
The estimated impact of the experiment of offering test preparation classes is:
= 9 - 1
= 8.