Briefly, as this is off-topic, and inline: Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Tue, May 31, 2016 at 11:32 AM, Dan Kolubinski <kolub...@lsbu.ac.uk> wrote: > That makes perfect sense. Thank you, Michael. I take your point about not > chasing the data and definitely see the risks involved in doing so. Our > hypothesis was that the first, second and fourth variables would be > significant, but the third one (intervention) would not be. That is **not** a legitimate scientific hypothesis. Post to a statistical list like stats.stackexchange.com to learn why not. Cheers, Bert I will > double-check the dataset to make sure that there are not any errors and > will report the results as we see them. I much appreciate you taking the > time! > > Best wishes, > Dan > > On Tue, May 31, 2016 at 12:02 PM, Michael Dewey <li...@dewey.myzen.co.uk> > wrote: > >> In-line >> >> On 30/05/2016 19:27, Dan Kolubinski wrote: >> >>> I am completing a meta-analysis on the effect of CBT on low self-esteem >>> and >>> I could use some help regarding the regression feature in metafor. Based >>> on the studies that I am using for the analysis, I identified 4 potential >>> moderators that I want to explore: >>> - Some of the studies that I am using used RCTs to compare an intervention >>> with a waitlist and others used the pre-score as the control in a >>> single-group design. >>> - Some of the groups took place in one day and others took several weeks. >>> - There are three discernible interventions being represented >>> - The initial level of self-esteem varies >>> >>> Based on the above, I used this command to conduct a meta-analysis using >>> standarized mean differences: >>> >>> >>> >>> MetaMod<-rma(m1i=m1, m2i=m2, sd1i=sd1, sd2i=sd2, n1i=n1, n2i=n2, >>> mods=cbind(dur, rct, int, level),measure = "SMD") >>> >>> >> You could also say mods = ~ dur + rct + int + level >> >> >>> >>> Would this be the best command to use for what I described? Also, what >>> could I add to the command so that the forest plot shows a sub-group >>> analysis using the 'dur' variable as a between-groups distinction? >>> >>> >> You have to adjust the forest plot by hand and then use add.polygon to >> add the summaries for each level of dur. >> >> >>> Also, with respect to the moderators, this is what was delivered: >>> >>> >>> >>> Test of Moderators (coefficient(s) 2,3,4,5): >>> QM(df = 4) = 8.7815, p-val = 0.0668 >>> >>> Model Results: >>> >>> estimate se zval pval ci.lb ci.ub >>> intrcpt 0.7005 0.6251 1.1207 0.2624 -0.5246 1.9256 >>> dur 0.5364 0.2411 2.2249 0.0261 0.0639 1.0090 * >>> rct -0.3714 0.1951 -1.9035 0.0570 -0.7537 0.0110 . >>> int 0.0730 0.1102 0.6628 0.5075 -0.1430 0.2890 >>> level -0.2819 0.2139 -1.3180 0.1875 -0.7010 0.1373 >>> >>> --- >>> Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 >>> >>> >>> >> So the totality of moderators did not reach an arbitrary level of >> significance. >> >> >>> From this, can I interpret that the variable 'dur' (duration of >>>> >>> intervention) has a significant effect and the variable 'rct' (whether a >>> study was an RCT or used pre-post scores) was just shy of being >>> statistically significant? I mainly ask, because the QM-score has a >>> p-value of 0.0668, which I thought would mean that none of the moderators >>> would be significant. Would I be better off just listing one or two >>> moderators instead of four? >>> >>> >> At the moment you get an overall test of the moderators which you had a >> scientific reason for using. If you start selecting based on the data >> you run the risk of ending up with confidence intervals and significance >> levels which do not have the meaning they are supposed to have. >> >> >> Much appreciated, >>> Dan >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >>> https://stat.ethz.ch/mailman/listinfo/r-help >>> PLEASE do read the posting guide >>> http://www.R-project.org/posting-guide.html >>> and provide commented, minimal, self-contained, reproducible code. >>> >>> >> -- >> Michael >> http://www.dewey.myzen.co.uk/home.html >> > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
