Chi square test for variance

03192015, 11:53 AM
(This post was last modified: 03192015 10:05 PM by salvomic.)
Post: #1




Chi square test for variance
Hi all,
in Prime Inference App we have to tests for Chi2 (chi square): Goodness of Fit and 2waytest... However I need to calc chi2 test having only s^2 and σ^2 (H_0: σ^2 = value, H_1: σ^2 ≠ value) (i.e. s^2 = 0.0153, σ^2 = 0.01, n=20) the test to confront with chisquare should be \[ X_{0}^{2}= \frac{(n1)s^{2}}{σ_{0}^{2}} \] (for my data I should have X^2= 29.07 against chisquare(19,10.05)=30.14 and then reject H_0)... Can I do something already with Inference app? If not I hope to see also this test Chi2 for variance added in Inference App (chi2 test section) in a next upgrade of the firmware... :) Thank you Salvo ∫aL√0mic (IT9CLU) :: HP Prime 50g 41CX 71b 42s 39s 35s 12C 15C  DM42, DM41X  WP34s Prime Soft. Lib 

03192015, 03:09 PM
(This post was last modified: 03202015 12:20 PM by salvomic.)
Post: #2




RE: Chi square test for variance
my first propose is this one.
chi2_variance() It calc X² test and compare with χ² (saying if H₀ is to be reject or not), then calc also p value and confidence interval... If you have other idea for improvement, please, suggest... Code:
Also, please, help: is it possible to display results graphically as in Inference in a normal program (not an App)? or help me to make ...an App I would indeed "mimic" the output of Inference... ∫aL√0mic (IT9CLU) :: HP Prime 50g 41CX 71b 42s 39s 35s 12C 15C  DM42, DM41X  WP34s Prime Soft. Lib 

03192015, 09:42 PM
Post: #3




RE: Chi square test for variance
I agree, this would be very useful to have Hypothesis Testing and Confidence Intervals for standard deviation/variance for 1 and 2 sample cases.
Interestingly, the TI84+ and Nspire calculators have the 2 sample FTest for standard deviation, but none of the other standard deviation Intervals or Tests. That always struck me as being odd to leave certain ones out. wes 

03192015, 10:03 PM
Post: #4




RE: Chi square test for variance
(03192015 09:42 PM)Wes Loewer Wrote: I agree, this would be very useful to have Hypothesis Testing and Confidence Intervals for standard deviation/variance for 1 and 2 sample cases. Indeed, Wes, you're right. ∫aL√0mic (IT9CLU) :: HP Prime 50g 41CX 71b 42s 39s 35s 12C 15C  DM42, DM41X  WP34s Prime Soft. Lib 

03192015, 10:45 PM
(This post was last modified: 03192015 10:47 PM by salvomic.)
Post: #5




RE: Chi square test for variance
Another improvement for Inference could be Prediction Interval (not Confidence Interval) having mean x̅ (x_bar) and standard deviation of the sample, s...
For now in Inference there is only Regression > Prediction Interval, but this estimation need to have two lists: Xlist and Ylist... ∫aL√0mic (IT9CLU) :: HP Prime 50g 41CX 71b 42s 39s 35s 12C 15C  DM42, DM41X  WP34s Prime Soft. Lib 

03202015, 06:55 AM
Post: #6




RE: Chi square test for variance
Xcas has the following commands for tests:
 chisquaret (chi2 test)  normalt (normal)  studentt (Student)  kolmogorovt (K.Smirnov)  wilcoxont (Wilcoxon) chisquaret takes 2 args: 2 samples or 1 sample and a distribution law (i.e. you can test adequation with more distributions than just the normal distribution). I don't think these commands are inside the Prime right now, might be an interesting addition... 

03202015, 10:20 AM
Post: #7




RE: Chi square test for variance
(03202015 06:55 AM)parisse Wrote: Xcas has the following commands for tests: thank you Parisse, I agree: why not include those (of some of them) tests in Prime? Especially in Inference app... Salvo ∫aL√0mic (IT9CLU) :: HP Prime 50g 41CX 71b 42s 39s 35s 12C 15C  DM42, DM41X  WP34s Prime Soft. Lib 

03202015, 04:50 PM
Post: #8




RE: Chi square test for variance
KolmogorovSmirnov test and Student test are also important and are used a lot so as parisse suggested it would be a great addition to include the whole patrisse's list of test:
 chisquaret (chi2 test)  normalt (normal)  studentt (Student)  kolmogorovt (K.Smirnov)  wilcoxont (Wilcoxon) 

03202015, 10:26 PM
Post: #9




RE: Chi square test for variance
(03202015 04:50 PM)Anders Wrote: KolmogorovSmirnov test and Student test are also important and are used a lot so as parisse suggested it would be a great addition to include the whole patrisse's list of test: yes, Anders, I agree! Another thing I think it should be included in Inference: Test F for variances of two population: here there is my proposal... ∫aL√0mic (IT9CLU) :: HP Prime 50g 41CX 71b 42s 39s 35s 12C 15C  DM42, DM41X  WP34s Prime Soft. Lib 

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