John is running a study on whether a particular SAT training class is effective. The students take the SAT before and after taking the class. The 95% confidence interval for the difference is scores (after - before) is [5, 15]. Which of the following is NOT true?

a. There is statistically significant evidence that the training class increases SAT scores.

b. The average increase in SAT score among the students was 10.

c. This is an example of a paired design.

d. The training class caused a big improvement in the students' SAT scores.