z value

  1. R

    Confusion between z and t values

    Hi, Alright so I have some confusion on when to use specific tests and the z vs t test. Given this example (not my homework) could someone please clarify. Alright say you have a random sample of size 200. You find the sample mean to be 10 and the sample standard deviation to be 5. What...
  2. K

    if z-value is a negative number, how can i calculate the Probability?

    Hello guys, :) I have an important question I want to ask. I have already searched the web and my statistics book but I can not find the answer :( I stumbled across this problem when preparing for my final from statistics and I can not figure out how we can get P=1 from a z-value=-10.6066...
  3. I

    How to find Z-value given probability?? PLEASE HELP

    Hi, I'm struggling on how to find the z value given the probability (working backwards using the table). Here's an example: The demand for a daily newspaper at a stand is known to be normlly distributed with a mean of 150 and a standard deviation of 25. How many newspaper should the...