SOLUTION: Find the mean, variance, and standard deviation for the following probability distribution. X= 3 6 9 12 15 Px=.15 .29 .30 .11 .15 I know to get the mean you multip

Algebra ->  Probability-and-statistics -> SOLUTION: Find the mean, variance, and standard deviation for the following probability distribution. X= 3 6 9 12 15 Px=.15 .29 .30 .11 .15 I know to get the mean you multip      Log On


   

Question 352210: Find the mean, variance, and standard deviation for the following probability distribution.
X= 3 6 9 12 15
Px=.15 .29 .30 .11 .15
I know to get the mean you multiply for example 3 x .15, 6 x .29, 9 x .30, and so on. But when I am crunching my numbers to try to get the standard deviation and variance, they are not coming out.
I really appreciate the help! =)
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Now that you have the mean, calculate the square of the difference between the x value and the mean, square it, and multiply by the probability.
VAR=sum%28%28x-mu%29%5E2%2AP%28x%29%29
.
.
sigma=sqrt%28sum%28%28x-mu%29%5E2%2AP%28x%29%29%29
.
.
mu=8.46
.
x1:%283-8.46%29%5E2%2A%280.15%29=4.472
x2:%286-8.46%29%5E2%2A%280.29%29=1.755
x3:%289-8.46%29%5E2%2A%280.30%29=0.087
x4:%2812-8.46%29%5E2%2A%280.11%29=1.378
x5:%2815-8.46%29%5E2%2A%280.15%29=6.416
Sum those values, that's the variance.
VAR=14.108
Take the square root of the variance, that's the standard deviation.
STDEV=3.756
Best way is to set up an EXCEL spreadsheet to crank through all of these operations.