# z value

1. ### 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. ### 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...