Question

80, 85, 72, 76, 95
Find the variance.

Answer 1

variance .... thats standard deviation right? or am i confusing it with something else

Answer 2

Variance the square of the standard deviation.

Answer 3

is*

Answer 4

yeah, I JUST read that lol

Answer 5

(80+85+72+76+95)
------------------ = mean
5

Answer 6

sum(x-mean)^2
-------------- = variance then
5-1

Answer 7

http://www.mathsisfun.com/data/standard-deviation.html

Answer 8

79.3 if I did it right

Answer 9

Why did you divide by 5-1?

Answer 10

yea tht's wht it is:79.3

Answer 11

becasue that the formula in my stat book for sample variance; I think population variance would be /5

Answer 12

What you used is 'S' which is an estimator of the population variance given a sample but to find the variance of this, sample, you divide by n.

Answer 13

why theres a diff between \(\mu\) and \(\bar x\), i got no clue

Answer 14

Mu just means population mean and x bar sample mean, it's useful to have to symbols if you're working with both at the same time.

Answer 15

yeah, but why is sample variance /(n-1); and population variance just /(N)?

Answer 16

hint out of these 4
1) 6.72
2) 63.44
3) 49.23
4) 7.96

Answer 17

The /(n-1) one estimates the variance of the population from a sample and the /n one finds the variance of a population exactly by measuring the whole population.

Answer 18

2 then; 2 relates to population variance

Answer 19

how do we determine when a set of data points relates to a sample or a population?

Answer 20

Yep, it's 2.

Answer 21

You have to read the question carefully. In this case, you're being asked to find the variance of the population: 80, 85, 72, 76, 95. In another question, you may given a sample and asked to estimate the variance of the population the sample is from, in that case, you'd use '/(n-1)'.