I Cant find the answer about the 10 year

if someone could help me would be great

Assume normal distribution. You basically need it to be under 50 inches for 9 years in a row and then ten inches the tenth year. So for the 9 years, left(Z = 2.5) then take that prob to the ninth power. Then multiply by right(Z = 2.5) and you have your prob.

thanks for replying

1. Where your Z come from?

2. Also why its necessary the 10inch on the last year


ty

hes wrong
the question is whats the probability of it taking over 10 years. which means it doesnt happen in the first 10 years. the Z is (50-40)/4 in other words the critical value minus the mean divided by the sd.
the answer is the probability of it raining under 50 inches for the first 10 years. so its left(z=2.5)^10


z=2.5 is going to be like ~99 percent (you have to look up exact value) and so its ~ .99^10

This post was edited by sentries on Nov 17 2014 01:14pm

Okay to the tenth power, you are right. And you don't multiply by the last one it's just left(z=2.5)^10

which is .9938^10 = 0.9397

It needs to take more than 10 years to hit 50 inches, so you basically just need to find out the odds of it being less than 50 for 10 years in a row. That's what is done here.

This post was edited by Dontrunaway on Nov 17 2014 01:58pm