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From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: sign test output |

Date |
Wed, 16 Jan 2013 09:33:16 +0000 |

In addition, it could be as or more useful to think in terms of confidence intervals. With this sample size and average, 0.5 lies well outside 95% intervals for the probability of being positive, and that is robust to method of calculation: . cii 346 221 -- Binomial Exact -- Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+--------------------------------------------------------------- | 346 .6387283 .0258248 .5856497 .6894096 . cii 346 221, jeffreys ----- Jeffreys ----- Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+--------------------------------------------------------------- | 346 .6387283 .0258248 .5871262 .6880204 . cii 346 221, wilson ------ Wilson ------ Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+--------------------------------------------------------------- | 346 .6387283 .0258248 .5868449 .6875651 Nick On Wed, Jan 16, 2013 at 9:13 AM, Maarten Buis <maartenlbuis@gmail.com> wrote: > 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. * * 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:*Nahla Betelmal <nahlaib@gmail.com>

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

**Re: st: sign test output***From:*Maarten Buis <maartenlbuis@gmail.com>

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