## chocolatechip_543 3 years ago The following table shows the probability distribution for a discrete random variable. X 13 16 18 21 23 25 26 31 P(X) 0.07 0.21 0.17 0.25 0.05 0.04 0.13 0.08 The mean of the discrete random variable X is 20.59. What is the variance of X? Round your answer to the nearest hundredth.

1. telliott99
2. hal_stirrup

$s2 = Σ ( x _{I} - x )2 / ( n - 1 )$

3. hal_stirrup

are you there??

4. chocolatechip_543

yes

5. chocolatechip_543

can you explain the equation a bit?

6. hal_stirrup

sure lets star with $\sum_{i=1}^{n}$

7. hal_stirrup

do you understand what this means?

8. chocolatechip_543

yes

9. hal_stirrup

good then$x_{i} -x$ xi is each value of your x value . -x really i cant use xbar because the keyboard is limited .. x bar is the average= $xbar=\sum_{i=1} x _{i}/n$

10. hal_stirrup

we are assuming that you have sample and not population as well !!!!

11. chocolatechip_543

alright..I'm a little lost now

12. hal_stirrup

tell me where.

13. chocolatechip_543

at the last part you posted

14. hal_stirrup

"we are assuming that you have sample and not population as well" that

15. chocolatechip_543

yes and before that

16. hal_stirrup

look. inorder to help you you need to be clear as to where are you not understanding . so i can help you better. thanks

17. chocolatechip_543

I'm sorry, I just don't understand it.

18. hal_stirrup

no need to be sorry . :)

19. hal_stirrup

have you done statistics before ?

20. chocolatechip_543

no, but this is in my algebra 2 work

21. hal_stirrup

thats cool/

22. hal_stirrup

do you now how to get the mean?

23. chocolatechip_543

yes

24. hal_stirrup

ok so were half way.

25. hal_stirrup

lets talk concept first. is that ok?

26. chocolatechip_543

sure

27. hal_stirrup

variance is the distance from the mean measured in squares. |dw:1343956195413:dw|

28. hal_stirrup

in you r case you have many data points. so really your job is fine all the distance from the mean and then sum them up and divide by the number of data point and minus 1.

29. hal_stirrup

s2=Σ(xI−x)2/(n−1) thats what this formula say.

30. chocolatechip_543

oh alright

31. hal_stirrup

share what your thinking if you like?

32. hal_stirrup

if you like to , be my fan and send my question and thoughts if you want and dont forget to click on best response . thanks @chocolatechip_543