# Simple Statistics Problem

1. Oct 6, 2009

### yopy

The question reads exactly as follows,

Find the appropriate values for #'s.

a) P(Z<#)=.9
b) P(|Z|<#)=.9

We are currently going over distributions, poissons, density functions and binomial stuff, someone referenced to Z-values from a ztable but i dont know if this is what the topic at hand is. Does anyone know what they are asking?

2. Oct 7, 2009

### jbunniii

I assume Z is some random variable. What is its probability distribution?

3. Oct 7, 2009

### HallsofIvy

Staff Emeritus
It looks to me like they are asking "for what value of "#" is the probability that z is less than # equal to .9?" and "for what value of "#" is the probability that |z| is less than # equal to .9?" The answer, of course, will depend on the probability distribution. Since you refer to "z values" and a "z table" I suspect you are talking about a "normal distribution". Here is a table for the normal distribution:
http://people.hofstra.edu/Stefan_Waner/realworld/normaltable.html [Broken]

Notice that this gives the probabilty that z is between 0 and the given number. To find the probabilty that z is less than a number, look up the value and add 0.5. To find the probability that |z| is than than the number, look up the value and multiply by 2.

Last edited by a moderator: May 4, 2017