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
Answer:
-29/6
Step-by-step explanation:
1 1/6=7/6
-3 2/3=-11/3
-11/3-7/6
-22/6-7/6=-29/6
Yes yes woeoshdenenejdjdjdjejejrjrrjekekekekekeek 30
The 3 sides should obey the Pythagorean Theorem
29^2 = 21^2 + 18^2
29^2 does not equal 441 + 324 = 765
29^2 = 841