Thank for all the help on the previous subject, now got one on distribution..
In an examination it is known that the distribution of marks is N (52,24)
a) what proportion of the marks will exceed 55?
b) what proportion of the marks will be less than 45?
c) if a grade A is awarded for the to p5% of marks, what is the minimum mark required in order to achieve a grade A?
d) the bottom 20% of the marks was graded as an F, What was the range of these marks?
Sorry for all the questions, had hundreds of these and stuck on a few of them :(
You probably have a table of values for the standard normal distribution N(0,1). Now if X = N(52,24) you can normalize
Originally Posted by jimmybob
where Z is standard normal N(0,1). Now you look for the corresponding value in table...
Using this you should be able to solve a-d.