- Thread starter ocean1
- Start date

Form the z table for standard normal curve, I am trying to find out the probability of z>1.65.

According to z table, z score of 1.65 is 0.4505

According to z table, z score of 1.65 is 0.4505

As such, can I say that the probablity of obtaining z value >1.65 is 0.4505?

Did I get it right?

Did I get it right?

Last edited:

According to z table, z score of 1.65 is 0.4505

Where did you get that number? The correct answer is 0.9505.

My guess is that ocean1 is using a z table that gives you the area between 0 and your z score. Those are probably the least common type of z-table but I've seen them before.

Ocean1: Note that P(Z < 0) = .5 [Can you see what that needs to be true?] Use that along with what your table tells you [ P(0 < Z < 1.65) = .4505] can you figure out how to get P(Z > 1.65)?

P(z < 1.65) is close to .9505 but P(z > 1.65) is definitely not .9505

To be honest, I haven't seen a z-table in years, nor have any of my students I think (well, it's at the end of their books but I doubt they bother to look). It's TI-83s all the way...

People still use TI-83s? Huh... alright.

One problem is of course that some students have a pretty good grasp of how the thing works, but no idea what they're doing.

1.65 is 0.4505 as you state. That means everything from the left of that line to the 50th percentile is 45.05% of the populations. In addition to that you have another 50% of the people below the 50th percentile. That's a total of 95.05% below this z score.

Your question was what is the probability of getting a score above this? So...

100-95.05=4.95% (.0495) which is what DancerTiffy gave you. It's good to remember how to do this because I now use a computer program to do all of these calculations for me.