basic statistics for the behavioral sciences
posted by jan on .
there are 80 students enrolled in statistics. (a)you and 11 other earned the same score. what percent of the class received your score? (b)forty percent of the class received a grade of C. how many students received a C? (c) only 7.5% of the class received a D. how many students is this? A student claims that .5% of the class failed. why is this impossible?

a) 11 + 1 (you) = 12. 12/80 = 0.15 = 15%
b)40% = 0.4, 0.4 x 80 = 32.
c) 7.5% = 0.075, 0.075 x 80 = 6
Also, 0.5% x 80 = 0.005 x 80 = 0.4 students, which doesn't make sense. 
fill in missing proportion for normal distribution.
1. .40
2. .10 
see a.) if .15 = 15%, which is correct, then .5 is 50% not .005, therefore, 4 students failed but, we have calculated that 65% of the students have a grade above failing. The claim that 50% failed is false, there is only 35% left who have a grade other than the D and some other grade different than the 15% that is, 12 of 80 or 12/80.

72%

If the class inclues you ... then how can it be a pool of 80 ? the pool would have to be 79 and only 11 students got your score ?