Z-scores for probability in tails


New Member
I haven't done any stats in years and now I am in a course for my grad program and I am so lost. My teacher is very confusing and I am trying my best to make sense of the way of going about finding z-scores in probability in tails. Do anyone know a good place that would illustrate the way to use the table and what the values of the tables are in layman's terms?

This is the type of problem that I am having problems with:

Trying to find the z-score for which a total probability of .02 falls more than z standard deviations (in either direction) from the mean, that is below mean-zo or mean+zo. Not sure how to type special characters but the o = standard deviations.

If anyone could help, I would greatly appreciate it. Getting past this type of problem would be huge for me.


For the probability of 96% ( 2% plus or minus ), Z is 2.05.
Please also note that Z scores for 99%, 95%, 90%, and 80% are 2.59, 1.96,1.64 and 1.28 respectively.