Maths help (1 Viewer)

[Farhanthestudent005]

How do I find the variance? Please help. I found the mean but I need to find the variance so I can find S.D as well. Someone please help. Thanks

 

[may22]

What topic is this and how come I don't remember ever learning it? I mean I did mean and SD in year 10, but not in year 11

 

[jimmysmith560]

Thank you @cossine for the correction and apologies for misreading the question.

μ = 25/5 = 5

x​	p(x)​	x^2 * p(x)​
3​	0.2​	1.8​
4​	0.15​	2.4​
5​	0.35​	8.75​
6​	0.3​	10.8​
7​	0.1​	4.9​
		Total: 28.65

Using

 

[cossine]

Data	xi - xbar	(xi - xbar)^2
3	-2	4
4	-1	1
5	0	0
6	1	1
7	2	4
Total: 25		Total: 10

Mean = 25/5 = 5


UsingView attachment 31790

I thought population standard deviation would be use?

 

[Trebla]

Find E(X) and E(X^2) (the probability weighted average of X and X^2 respectively), then use the fact that Var(X) = E(X^2) - [E(X)]^2

 

[ExtremelyBoredUser]

What topic is this and how come I don't remember ever learning it? I mean I did mean and SD in year 10, but not in year 11

Maths Advanced Year 11 Probability

 

[ExtremelyBoredUser]

An alternative method to using the formula for finding Var(X) is calculating (X-E(X))^2*p(x) under the table and the sum of the values is the variance.

 

[may22]

Maths Advanced Year 11 Probability

Either it's because I haven't started this week's homework, or we haven't gotten to this point yet....but I have not come across that...I'll be on the lookout haha

 

[may22]

@Farhanthestudent005 @ExtremelyBoredUser when are your prelims starting?

 

[ExtremelyBoredUser]

@Farhanthestudent005 @ExtremelyBoredUser when are your prelims starting?

Some of our prelims got converted into assignments so theres only 4 exams for me. They're all starting/due week 9ish.

 

[may22]

Some of our prelims got converted into assignments so theres only 4 exams for me. They're all starting/due week 9ish.

Oh luckyy, I've got 7 exams and they start next week, end in week 9