Thread: I need some help

I am having trouble getting the mean and standeard deviation. could you please show me how ? thanks

perscription data
0.4-1.1
1.2-1.9
2.0-2.7
2,8-3.5
3.6-4.3
Frequency
2
2
4
3
9

whats wrong?

the mean is the sum of the mid points of each class times the class frequency divided by the total frequency

and then the standard deviation is

its just a simple formula where are you having trouble ?

how do i get the class mid points ?

take the mean of the upper and lower boundaries.

for example