P-value

[robertrao]

Hi Team,

I am comparing two means and calculating Z score and then the p-value.

If i get the p-value less than 0.05 will I call it "YES THERE IS SIGNIFICANT DIFFERENCE"

OR

NO, THERE IS NO SIGNIFICANT DIFFERENCE???

Please give me some idea.

Regards

[Ksharp]

What is your SAS code ?

If i get the p-value less than 0.05 , I can call it "YES THERE IS SIGNIFICANT DIFFERENCE" .

But I will more trust confidence interval  .

[ballardw]

You should decide what would be a significant difference BEFORE the test and know why you chose that value.

[rnmishra]

The P-value =0.05, is not always useful. First go back to your problem and decide how accurate you want to be. Then decide on your p-value- not necessarily 0.05.

Then go ahead with what you are doing.

These are just my thoughts.

Thanks.

[Doc_Duke]

There is a lot more to interpreting statistical significance than just looking at the p-value.  See, for instance,

http://ceaccp.oxfordjournals.org/content/7/6/208.full

Your second claim, "NO, THERE IS NO SIGNIFICANT DIFFERENCE???" is a statement about the type II error and not about the type I (p-value) error.  The correct interpretation statement is

"We failed to determine statistical significance.", which is much weaker.

Doc Muhlbaier

Duke

[SteveDenham]

Great reference, Doc.  I want to send it to all of the toxicology study directors

Steve Denham