Normal Distribution

02192019, 12:24 AM
Post: #1




Normal Distribution
I high school student posted a question under my YouTube video on the Prime yesterday, saying she is trying to find the best way to calculate "Normal Distribution." Today she said, "I found a slow but effective way to calculate normal distribution graphically, you can use NORMALD(mean, std deviation,x) in Function Symbolic View and use signed area for the upper and lower limits in plot mode. Also i read that you can use NORMAL_CDF(mean, std deviation, lower, upper) but this way is only effective symbolically."
What is the best way on the Prime to calculate Normal Distribution? 

02192019, 01:38 PM
Post: #2




RE: Normal Distribution
Yes, the CDF is the definite integral of the PDF for all distribution models.


02192019, 11:55 PM
Post: #3




RE: Normal Distribution
But note that she said this:
“You can use NORMAL_CDF... but it is only effective symbolically.” That statement implies she is looking for a nonsymbolic solution. What thoughts do you have on that? Thank you. 

02202019, 01:34 PM
(This post was last modified: 02202019 01:54 PM by Tim Wessman.)
Post: #4




RE: Normal Distribution
She is probably in the CAS view and using whole numbers only...
These are primarily numeric commands and the fact that she is getting symbolic results is by FAR the most unlikely case since you never have whole, exact numbers in real use cases. Home screen, use ANY of the _CDF commands and you get numeric results. NORMALD_CDF(0,1,0) > .5 or in the CAS screen, add a decimal after any number to make it "approximate" and you get an immediate numeric result. NORMALD_CDF(0.,1,0) > .5 Also, remind her that she can go to the MATH>Probability>Cumulative, select the one she wants and press help to get help on it with examples. TW Although I work for HP, the views and opinions I post here are my own. 

02202019, 04:11 PM
Post: #5




RE: Normal Distribution
Thanks Tim, it was useful to me as well.
Cheers 

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