Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

From |
David Hoaglin <dchoaglin@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: GLLAMM: logitic regression interaction non signficant but lincom gives signficant result |

Date |
Sat, 19 May 2012 16:35:32 -0400 |

Abdelouahid, You are confused because you see a contradiction where there is none. A similar situation can arise in comparing the means of several groups in a one-way analysis of variance. The F-test can reject the hypothesis that all the true means are equal; but, when the means are put in increasing order, all the comparisons between adjacent means can be non-significant (allowing appropriately for the multiple comparisons). David Hoaglin On Sat, May 19, 2012 at 1:22 PM, Abdelouahid Tajar <a_tajar@hotmail.co.uk> wrote: > Thanks for all the comments and the references, > > Indeed the interaction term tests if the two slopes are significantly different from each other and you only get the slope and its confidence interval for the reference group, however lincom " computes point estimates, standard errors, t or z statistics, p-values, and confidence intervals for linear combinations of coefficients after any estimation command". > > Because I wanted to compute the slope of group1 I run the lincom, BUT, the lincom result are in contradiction ( in terms of significance) with the interaction result in the main model. The main model says that the two slopes are not significantly different (interaction non significant0 and because the slope of the reference is not significantly different from 0 this should mean that the slope of group1 is also not significantly different from 0 but the lincom result shows that the slope of group 1 is actually significantly different from 0, hence my confusion. > > Denominator in gllamm is for the number of trials, hence for a Bernoulli distribution denominator is set to be 1. > See Page 374 in S. Rabe-Hesketh and A Skrondal: Multilevel and longitudinal modeling using stata. > > I think the contradiction between the non significance result in the interaction term and the significance result in the lincom is not necessarily related to gllamm. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: GLLAMM: logitic regression interaction non signficant but lincom gives signficant result***From:*Abdelouahid Tajar <a_tajar@hotmail.co.uk>

**st: RE: GLLAMM: logitic regression interaction non signficant but lincom gives signficant result***From:*Kieran McCaul <kieran.mccaul@uwa.edu.au>

**RE: st: RE: GLLAMM: logitic regression interaction non signficant but lincom gives signficant result***From:*Abdelouahid Tajar <a_tajar@hotmail.co.uk>

**Re: st: RE: GLLAMM: logitic regression interaction non signficant but lincom gives signficant result***From:*brendan.halpin@ul.ie (Brendan Halpin)

**Re: st: RE: GLLAMM: logitic regression interaction non signficant but lincom gives signficant result***From:*Joerg Luedicke <joerg.luedicke@gmail.com>

**RE: st: RE: GLLAMM: logitic regression interaction non signficant but lincom gives signficant result***From:*Abdelouahid Tajar <a_tajar@hotmail.co.uk>

- Prev by Date:
**Re: st: RE: GLLAMM: logitic regression interaction non signficant but lincom gives signficant result** - Next by Date:
**st: stratification matching** - Previous by thread:
**Re: st: RE: GLLAMM: logitic regression interaction non signficant but lincom gives signficant result** - Next by thread:
**RE: st: RE: GLLAMM: logitic regression interaction non signficant but lincom gives signficant result** - Index(es):