Math probability question help
Hello everyone, I was having a bit of trouble on a question regarding probability. Hoping someone understands it and might be able to help me reach the answer!
The question is:
Let the random variable X represent the profit made on a random clothing store on Main Street. Assume X is normal with a mean of $360 and a standard deviation
of $50.
31. What is P(X > $400)?
A) 0.2119 C) 0.7881
B) 0.2881 D) 0.8450
The answer here is A but I have no idea how to reach it. Any help would be appreciated.
March 14, 2012
1 Comment • Newest first
[quote=ShockPenguin]Find X's distance from the mean in terms of its standard deviation. In other words, let X = mean + Z * s.d.
Now find the z0 such that x = mean + z0 * s.d.
Then use a table (a calculator, Excel, etc. would make it easier if you're allowed to use them) to find P{z < z0}. Some tables call this Phi(z0).
Subtract from 1 and you should get P{Z > z0} = P{X > 400}.[/quote]
ahh cool thanks!