Answer:

--- Variance
Step-by-step explanation:
Given

Solving (a): Calculate the mean.
The given data is a grouped data. So, first we calculate the class midpoint (x)
For 51 - 58.

For 59 - 66

For 67 - 74

For 75 - 82

For 83 - 90

So, the table becomes:

The mean is then calculated as:



-- approximated
Solving (b): The sample variance:
This is calculated as:

So, we have:


-- approximated
IT IS 80 PLS MARK MEH BRALIEST:):):):):):):): also I did the this
I think It would be -4-(-8)/2-(-9)=-4+8/2+9=4/11 is the equation by using y2-y1/x2-X1
Sorry If I'm wrong.
I believe it’s 36 inches hope this helps