P Value
Six Sigma – iSixSigma › Forums › Old Forums › General › P Value
 This topic has 6 replies, 6 voices, and was last updated 15 years, 8 months ago by EdG.

AuthorPosts

December 3, 2006 at 5:59 pm #45412
Tahir MasoodMember@TahirMasood Include @TahirMasood in your post and this person will
be notified via email.We reject null ypothesis when the p value is less than 0.05 ,but what happens when it is equal to 0.05.Do we still reject the null hypothesis or is it other wise.
Help me and oblige.0December 3, 2006 at 7:08 pm #148356You said “We reject null ypothesis when the p value is less than 0.05 ” In this instance p = .05. If p = .05 then p is not less than .05 therefore you cannot reject the null given that your rejection criteria was that you would reject if and only if p < .05.
0December 3, 2006 at 7:46 pm #148358Lol, is this a onesided or twosided hypothesis?
0December 3, 2006 at 8:12 pm #148359
Ken FeldmanParticipant@Darth Include @Darth in your post and this person will
be notified via email.The real answer is, “It depends”. The .05 is just a guideline. Since you could just have easily used p=.10 or .08 or any number, it is just a guideline for you to make a decision. In fact, .05 is pretty restrictive and if your data is sloppy you might even use p=.15. If you have a better understanding of what the p value really means you might be able to understand why judgement is sometimes called for and not just strict adherance to a guideline and whether the p value equals it or is less/greater than.
0December 3, 2006 at 10:01 pm #148365You can set it at any value you want, depending who you are trying to fool … common practise by drug companies.
0December 4, 2006 at 1:54 am #148366
Ken FeldmanParticipant@Darth Include @Darth in your post and this person will
be notified via email.LOW BLOW!! Not sure that the FDA would approve a drug with a p value of .15. They are usually lower than that….a good bit lower.
0December 4, 2006 at 3:58 am #148367Generally, one rejects the null hypothesis if the pvalue is smaller than or equal to the significance level, often represented by the Greek letter á (alpha). If the level is 0.05, then the results are only 5% likely to be as extraordinary as just seen, given that the null hypothesis is true.
Based upon your own statement you are rejecting null hypothesis when the p value is less than 0.05 so your results are 4.99999% likely to be as extraordinary as just seen, given that the null hypothesis is true.0 
AuthorPosts
The forum ‘General’ is closed to new topics and replies.