# p value = 0 ?

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• #44683

MC
Participant

I would like to know, what does exactly a p value of null mean. I´m wondering if the programs performed well! Is it perhaps rather an indication that my objects of study are more than highly significant, i.e. totally different? Should I better make further test in order to get some positive value, although it will be very small?Thanks!

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#143743

Picklyk
Participant

Hi MC,
If the p is below 0.05 you can say that based on your test of a sample, looking at the population your subgroups are significantly different from one another.
If you have a p value of 0 it just means that there is 0% chance of you making an alpha error; meaning there is a 0 per cent chance of you stating that the subgroups of your population are different when in fact they are not.
Jay

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#143745

Quainoo
Member

I have a feeling that the p value cannot really be equal to zero.
It can get very close to it (very small value) but not exactly zero.
Vincent

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#143755

Dr Casey
Participant

Diagnosis – urethritis.

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#143756

MC
Participant

Thank you Jai and Vincent for your answer. Now I will sleep better, although I had also the same feeling as Vincent. As p is an area, perhaps you can say it tends to null when x tends to infinite. I guess, the statistical programs say p = 0 depending on how did you set your number of decimals.
Any way, I think we three agree.Thanks :))

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#143757

Orang_Utan
Participant

How you get P value=0? No way!

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#143766

Szentannai
Member

Hi,
AFAIK the statistical programs will display tge p value to a precision of 3 or decimals only. If p < 0.0001 all they will show is a zero. So what you see probably means only that the p is so small that the program did not bother to print the exact value and not that it is strictly 0.Regards
Sandor

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#143767

MC
Participant

Hello! and thank you for the answers regarding the p = 0. Jai, I could sleep better, thinking that my populations were in fact different! Vincent, I agree with you also, perhaps it´s a matter of properly defining. As p is in fact an area, would it be propperlier to say that p tends to null if X tends to infinite? (also for Orang) Thank you Sandor, I was also looking for some explanation – experience like that. I also agree with you, but look, the precission of my programs is like this:p 0.00795
p 0.00000 So the p value must be really very small, don´t you agree!?Have a nice sunday forum!

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#143769

Szentannai
Member

Hi Mc,
I also think that your p value is very small but not zero.
Have a nice weekend too!
Regards
Sandor

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#143941

Ron
Member

Hi,
The p value is used to determine if enough evidence exists to reject the null hypothesis in favor of the alternate hypothesis.
The p value is the probability of incorrectly rejecting the null hypothesis.
Simply remember, “if p is low (often <0.05) Ho must go."
Also, we never “accept” the null or alternate hypothesis… rather we “reject” or “fail to reject.”  This is a common error I have seen many new practitioners make.
Finally, I have seen the discussion below of whether p can be equal to 0 or very close to zero… the answer is yes it can and I can send actual data sets to prove this.  Don’t fret over this… else you run the risk of entering statistical analysis paralysis.
I hope this helps.

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#143951

Clowers
Participant

Use the P value as the percentage. If the P=0, subtract that from 100% and you are 100% confident that there is a statistical significance in the data you tested. Rejecting the NULL (that there is no difference) and ACCEPTING the alternative (that there is a difference) P=0.05, then you are 95% confident that the data is statistical. if the P=.5, then 50% really isn’t statistically significant.

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#145677

Bode
Participant

You sound like one of my instructors.  Have you ever been to Suffolk, VA?

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#145679

Ron
Member

No, never taught in the great state of VA.  But glad to hear your instructor and I agree!
Ron

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#171391

arghh
Participant

The P Value should not be ‘Null’ it is zero.  There’s a difference.

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#171419

Outlier, MDSB
Participant

I have 2 questions:
1. What does your response mean? It doesn’t make sense.
2. Why are you randomly responding to a 2-year old post?

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