Question

The following table gives the scores of 30 students in a mathematics examination.

90–99 80–89 70–79 60–69 50–59
6 7 13 3 1
Find the mean and the standard deviation of the given data. Hint: Assume that all scores lying within a group interval take the middle value of that group. (Round your answers to two decimal places.)

I got 6 for the mean and 4.1 for the standard deviation. Is this correct?

Answer 1

doesnt look right

Answer 2

90–99 80–89 70–79 60–69 50–59
6 7 13 3 1

Answer 3

FIrst row represents "marks of students"

Answer 4

second row represents "number of students"

Answer 5

i said it doesnt look right cuz :
since the marks are ranging between 59-99,
for mean, u MUST get some number between 59 and 99

Answer 6

getting wat im saying ha ? :)

Answer 7

Ohh ok I think so..

Answer 8

here is how u calculate mean :
http://www.wolframalpha.com/input/?i=%2894.5*6+%2B+84.5*7+%2B+74.5*13+%2B+64.5*3+%2B+54.5*1%29%2F%286%2B7%2B13%2B3%2B1%29

Answer 9

94.5, 84.5, 74.5, 64.5, 54.5 ?

Answer 10

those are the "mid values" of ranges

Answer 11

Ok, so for 94.5, I would list it 6 times?

Answer 12

90 + 99
------ = 94.5
2

Answer 13

yes, u multiply it wid # of students

Answer 14

94.5 * 6

Answer 15

and do the same for other columns as well,
and add them all
and divide the final sum wid total # of students

Answer 16

Got it, thanks! :)

Answer 17

np :)
u knw how to take standard deviation ?

Answer 18

Yup :)

Answer 19

okie good :)