Seven students take a speed reading course in order to improve their reading ability. The reading scores of the seven before and after taking the course are given below: Person 2 4 5 6 x Test Score (Before) 350 371 360 400 450 389 410 y Test Score (After) 370 366 365 413 440 420 419 Note that n = 7. We will define d1 = x1 - y1. After doing the appropriate calculations, we find that . d = -9 SA = 14.12 Find the 80 % confidence interval for mean of the differences, Hd