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From |
Maarten Buis <maartenlbuis@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: sign test output |

Date |
Wed, 16 Jan 2013 10:13:27 +0100 |

On Wed, Jan 16, 2013 at 9:38 AM, Nahla Betelmal wrote: > I have generated this output using non-parametric test "one sample > sign test" with null: U=0 , & Ua > 0 > > However, I do not understand the output. where is the p-value? is it > 0.5 in all cases or the 0.000 ( as in the first and third cases) and > 1.000 as in the second case? > >. signtest DA_T_1= 0 > > Sign test > > sign | observed expected > -------------+------------------------ > positive | 221 173 > negative | 125 173 > zero | 0 0 > -------------+------------------------ > all | 346 346 > > One-sided tests: > Ho: median of DA_T_1 = 0 vs. > Ha: median of DA_T_1 > 0 > Pr(#positive >= 221) = > Binomial(n = 346, x >= 221, p = 0.5) = 0.0000 The p-value is the last number, so in your case 0.0000. The stuff before the p-value tells you how it is computed: it is based on the binomial distribution, and in particular it is the chance of observing 221 successes or more in 346 trials when the chance of success at each trial is .5. For this tests this chance is the p-value, and it is very small, less than 0.00005. If you type in Stata -di binomialtail(346, 221, 0.5)- you will see that this chance is 1.381e-07, i.e. 0.00000001381. Hope this helps, Maarten --------------------------------- Maarten L. Buis WZB Reichpietschufer 50 10785 Berlin Germany http://www.maartenbuis.nl --------------------------------- * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: sign test output***From:*Nick Cox <njcoxstata@gmail.com>

**References**:**st: sign test output***From:*Nahla Betelmal <nahlaib@gmail.com>

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