Question

a school principal claims that grade 11 have a mean grade of 86 with a standard deviation of 4. suppose that the distribution is approximately normal, what is the possibility that a randomly selected grade will be less that 84?

Answer 1

z=(82–86)/4 = -1

z=(90–86)/4= 1

P(82<x<86) = 0.34134

P(86<x<90) = 0.34134

P(82<x<90) = 0.34134+0.34134 = 0.68268

Answer 2

I'm not sure, but I think is this