Stats question

[SlamminP]

The mean revenue from a restaurant is $1380 per day. The standard deviation of this revenue is $100. The boss forgot to take into account sales tax, which is 15% ($1380 is revenue before tax). What is the mean and standard deviation of revenues net of sales tax?

Anybody?

[Dan.]

a*(b+c) = (a*b) + (a*c)

That should get you started.

[SlamminP]

[ QUOTE ]
a*(b+c) = (a*b) + (a*c)

That should get you started.

[/ QUOTE ]
Thanks but nope.

[BlueBear]

Let x be a distribution and a is a constant.

mean(ax) = a * mean(x)
sd(ax) = a^2 * sd(x)

I'm only 99.9% sure, so you should go to http://en.wikipedia.org/wiki/Standard_deviation to check the basic definitions of SD and to see if you work out the two above equations for yourself.

Also, most basic statistic textbooks should have the two above relations buried somewhere inside.