# Ways of calculating Mean and Variance

• Oct 18th 2009, 01:35 AM
davidrocastle
Ways of calculating Mean and Variance
Hello i am looking at ways to calculate the mean and variance of X in this instance?

A footballer out injured has made arrangement wit the club doctor whereby in a given month he visit a knee specialist (at most one) if he has severe knee pain. The chances of having the pain in a given month 0.3 and such pains fo not affect in any pain occuring.

X = number of visits to knee speicialist in a typical year
• Oct 18th 2009, 02:11 AM
mr fantastic
Quote:

Originally Posted by davidrocastle
Hello i am looking at ways to calculate the mean and variance of X in this instance?

A footballer out injured has made arrangement wit the club doctor whereby in a given month he visit a knee specialist (at most one) if he has severe knee pain. The chances of having the pain in a given month 0.3 and such pains fo not affect in any pain occuring.

X = number of visits to knee speicialist in a typical year

X ~ Binomial(n = 12, p = 0.3)
• Oct 18th 2009, 02:44 AM
davidrocastle
Thanks Mr Fantastic

Could i check here, in one of the similar examples in a book, the mean is calculated as follows:
Mean1(attachement) and Mean2(attachment) for X ~ Binomial(n = 12, p = 0.3).

Which one is correct?

Attachment 13414

Attachment 13415
• Oct 18th 2009, 04:25 AM
mr fantastic
Quote:

Originally Posted by davidrocastle
Thanks Mr Fantastic

Could i check here, in one of the similar examples in a book, the mean is calculated as follows:
Mean1(attachement) and Mean2(attachment) for X ~ Binomial(n = 12, p = 0.3).

Which one is correct?

Attachment 13414

Attachment 13415

For Binomial(n, p) the mean is np and the variance is np(1-p).