Check out some similar questions!

krispykruller · Mar 6, 2009, 02:59 PM

Hello :D

I need some help with my statistics homework assignment. The question is... The number of suits sold per day at a retail store is shown in the table, with the corresponding probabilities

Number if suits sold, X 19 20 21 22 23
Probability, P(X) 0.2 0.2 0.3 0.2 0.1

Could someone please teach me how to find the mean, variance, and standard deviation of this data?

Thank you

galactus · Mar 6, 2009, 03:49 PM

Yes, it's easy. This is a "discrete non-binomial distribution".

Code:

   x         P(x)
-------------------
 19           .2 
 20           .2
 21           .3
 22           .2
 23           .1

For the mean:

${\mu}=\sum xP(x)$

That is, multiply the x by its P and add them up.

Variance:

${\sigma}^{2}=\sum (x-\mu)^{2}P(x)$

Once you have your mean, subtract it from each x, square it, multiply by its probability. Add them all up.

standard deviation:

$\sqrt{{\sigma}^{2}}$

Let me know what you get and we can check it.