Question

The marks obtained by students of a class in a test are normally distributed with a mean of 60 marks and a standard deviation of 5 marks.

About what percent of students have scored between 55 and 65 marks?
a.
2.5
c.
47.5
b.
34
d.
68

Answer 1

Again are you looking for answers or for help?

Answer 2

help to get the answer

Answer 3

So what is the mean of the marks?

Answer 4

60

Answer 5

And the standard deviation is?

Answer 6

5

Answer 7

So how many standard deviations above the mean is 65?

Answer 8

55

Answer 9

no...how much is 65 bigger than 60?

Answer 10

5

Answer 11

Right and that is equal to the size of the standard deviation so we say that 65 is 1 standard deviation larger than the mean (60)...Do see what I mean?

Answer 12

In other words 70 would be 2 standard deviations larger than the mean (60)

Answer 13

so D

Answer 14

Yes.

Answer 15

Good job.