Step-by-step explanation:
According to normal distribution curves following a bell curve formula, it is followed that
34% of people will lie between Mean point and one positive standard deviation
34% of people will lie between Mean point and one negative standard deviation
14% of people will lie between Mean point and two positive standard deviation
14% of people will lie between Mean point and two negative standard deviation
2% of people will lie between Mean point and three positive standard deviation
2% of people will lie between Mean point and three negative standard deviation
Now following this principle, we are given that mean score is 80 and standard deviation is 8, hence the interval for grades would be;
Grade A ; Score greater than 96
Grade B : Score greater than 88 and less than or equal to 96
Grade C : Score greater than 80 and less than or equal to 88
Grade D : Score greater than 72 and less than or equal to 80
Grade E : Score greater than 64 and less than or equal to 72
Grade F : Score less than 64
