Answer:
E(X) = 17.4
Step-by-step explanation:
We can calculate the expected value of a random X variable that is discrete (X takes specific values ) as:
E(X) = ∑xp(x) where x are the specific values of x and p(x) the probability associated with this x value.
In this way the expexted value is
E(X) = ∑xp(x) =(16*0.6)+(18*0.3)+(20*0.2) = 8+5.4+4 = 17.4
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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
for an angle of 780°, we can say that is really a 360° + 360° + 60°, so two full revolutions plus an extra 60°. Check the picture below, with the coterminal in green.