An example of how to calculate a z score.

z scores, statistics, probability

[shun]

This is the most straight forward version of this I've seen. No b.s. and no hard to understand accents

[richellelyon]

As an instructor in statistics, I frequently recommend this video. So clear and yet so brief. Nice visual representation of the concept!

[statisticsfun]

@whitedaisez

There is a table in the back of your book usually called a normalized table or a normal probabilities. .34 is the area between the mean and 1 standard deviation away. z scores are standard deviations. So 1 z score is 1 standard deviation away.

[statisticsfun]

@Harleybabe95667 Each table, in the back of your book is slightly different. What your table is telling you is all the area of the bell curve to the left of z = 1. This means that the area between the mean and 1 is .8413 - .5000. .5000 is the area from the mean to the far left side of the curve.

[statisticsfun]

@leotakesleo you have to solve for the sample mean. The equation is z score = (sample mean (x) - population mean (u) )/standard deviation. It may be easiest to start with a z score of 4 and work backwards. So if I divide up 0 to 4 at .5 then I will get 8 intervals. The z scores become (.5, 1, 1.5, 2, 2.5, 3, 3.5, 4). Now solve for the sample mean at each z score.

.5 = (x - 2)/.2 ; x = 2.1
1 = (x -2)/.2 ; x - 2.2
1.5 = (x-2)/2 ; x =2.3
and so it goes....

[statisticsfun]

@whitedaisez I know this stuff can be really frustrating. I created a video on my channel statisticsfun "Understanding Normalized Tables" that would help you. I can't seem to add a link to the video.

[maryc.d.]

Very helpful! On the other hand it would've helped to clarify or explain how you got .34 or 34%. It took me a while to understand that part.
FOR THOSE OF YOU WHO DON'T UNDERSTAND, HERE IT IS:
It is by subtracting the z-scores of 49 and 47.
...so looking up the values on TABLE A it is: .5000-.1587= .34 =]

[statisticsfun]

@Harleybabe95667 I know this stuff can be really frustrating, so I created a video "Understanding Normalized Tables" I can't seem to add a link, but you can see my video on my channel statisticsfun.

[rubixide]

Nice video with nice visuals. Remember that if you are using a SAMPLE and using x-bar for average, then you should also be using your sample standard deviation "s" instead of population standard deviation "sigma"

[TimmysMummy]

simple and clear... sooo useful. Thankyou very very much. x

[MoreKevinLiang]

Z score charts for -1 is 0.1587, or 15.87% of the curve from the left.
0.84, or 84% is attained by subtracting 15.87 from 100, to get the area to the right of 10.

In introductory stats courses, you probably don't need to find 0.34, which is the area from 10 to 15.

[statisticsfun]

I just added a link to an entire playlist on z scores in the video description of this video.

[PassaFloraElle]

BEST VIDEO. very clear. THANK, YOUUU!!!

[brashboy]

it has been said before, but brilliant
thank you so much

[metesables]

Good evening sir, I have a problem that I cant find a solution. It says to find the area between a raw score of 110 and 125 in a distribution with a mean of 100 and a standard deviation of 10. We know that z score 1 = 34.13 and z score 2 = 13.59. According to the problem, z score 2.5 = 15.25. My question is how do we know that 2.5 is = to 15.25. Thank you!!

[DannyDChung]

I love your videos but why is it that so many of your videos have audio that is playing on one side only? Drives me nuts!

[my_username_was_taken]

Watching several videos...Do you ever explain how to find the area? Or do you always just say look in your book?? A book I don't have.

[memphisdime]

I have problem: my mean is 500 and the standard deviation is 100, and trying find where the percentage falls above 550...i dont understand

[whitedaisez]

under 1 in my z score table has 0.8s not 0.3s. can someone plz help. nobody explains how to get this 0.34!

[statisticsfun]

@Harleybabe95667 Each table, in the back of your book is slightly different. What your table is telling you is all the area of the bell curve to the left of z = 1. This means that the area between the mean and 1 is .8413 - .5000. .5000 is the area from the mean to the far left side of the curve.