Alright, I'm in AP Stats, and tomorrow we have a test on z-scores, distribution, density curves, normal curves, and percentiles, etc. etc
What I don't get is, how is a normal curve laid out? like I don't understand how you shade the curve, I get neg. is on the left, pos, on the right. But where are the # values?
Also, I understand z-scores but i always mess up problems with z-scores. I mess up the %'s. Is there tips on how to do these problems? and can i do this on my calculator?
Thanks a bunch, p.s if you know any websites that help out it would be much appreciated!
What I don't get is, how is a normal curve laid out? like I don't understand how you shade the curve, I get neg. is on the left, pos, on the right. But where are the # values?
Also, I understand z-scores but i always mess up problems with z-scores. I mess up the %'s. Is there tips on how to do these problems? and can i do this on my calculator?
Thanks a bunch, p.s if you know any websites that help out it would be much appreciated!
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Alright I'm in AP Stat too and we have already covered this so I'll give you some facts that could help you.
- Z score is the # of standard deviations an observation is away from the mean.
- In a normal density curve 68% of all observations will fall within 1 standard deviation of the mean or Z = 1 /-1
- Same as above only difference is 95% of all observations will fall within 2 standard deviations or Z=2/-2
- Same as above again only 99.7% of all observations will fall within 3 standard deviations or Z=3/-3
- In order to calculate the Z score by hand you use the formula (observed X - mean) / standard deviation
- After calculating the Z score you can go to 2nd distribution, normalcdf ( on the ti-84. This will help you find the percentile that the observation is on. To do this put in a really low Z like -100 and then put a comma (,) and then your Z score that you found. This will give you the percent of observations less than your observation. To find the percent greater than your observaton do the same thing only instead of putting a really low Z first put your observed Z score first comma a really high Z like 100.
Hope this helps some It's a lot to explain. Good luck
- Z score is the # of standard deviations an observation is away from the mean.
- In a normal density curve 68% of all observations will fall within 1 standard deviation of the mean or Z = 1 /-1
- Same as above only difference is 95% of all observations will fall within 2 standard deviations or Z=2/-2
- Same as above again only 99.7% of all observations will fall within 3 standard deviations or Z=3/-3
- In order to calculate the Z score by hand you use the formula (observed X - mean) / standard deviation
- After calculating the Z score you can go to 2nd distribution, normalcdf ( on the ti-84. This will help you find the percentile that the observation is on. To do this put in a really low Z like -100 and then put a comma (,) and then your Z score that you found. This will give you the percent of observations less than your observation. To find the percent greater than your observaton do the same thing only instead of putting a really low Z first put your observed Z score first comma a really high Z like 100.
Hope this helps some It's a lot to explain. Good luck