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
-7 - 8 - (-8) - 7 × 0(14) - 14 - 30
(I think that's what that says)
Do PEMDAS
0(14) = 0
-7 × 0 = 0
You're left with -7 - 8 - (-8) - 14 - 30
Go from left to right
-7 - 8 = -15
-15 - (-8) = -7
-7 - 14 = -21
-21 - 30 = -51
159.98 divided by 6 is 26.66, hopefully this is correct...