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From |
kathryn dennick <kath_dennick@hotmail.com> |

To |
"statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |

Subject |
Re: st: Re: "Meta-analysis" of Proportions |

Date |
Sun, 21 Apr 2013 07:10:25 -0700 |

Thank you, both. I don't use Stata, I know very little about it and was lead to believe by a course tutor that my query was not possible and hence would not be covered by FAQs and the like. Instead, I was advised to post here. I also used columns in an attempt to be explicit about the way in which I was entering data. Yes, variables are more appropriate. Thank you. I also didn't realise my message would go straight to the list, rather I thought the text relating to my query might be extracted as I submitted it to an email address which I presumed might be for for moderation or the like. My apologies, had I realised it would have been tidier and clearly marked etc. Many thanks for your help. I very much appreciate it. Best wishes, Kathryn Sent from my iPhone On 21 Apr 2013, at 06:38, "Steve Samuels" <sjsamuels@gmail.com> wrote: > Welcome to Statalist, Kathryn. > > You'd do much better if you: > 1. Read the FAQ > 2. Put a subject into your emails > 3. Spelled Stata correctly -not "STATA" (see the FAQ) > 4. Use Stata, not spreadsheet, terms: you have "variables" that you are inputting, not "columns" > > Unlike a meta-analysis of a causal effect, there is no reason to > believe that proportions from the different studies will be identical, or > even similar. So it is a bad idea to pool studies (add numerators & > denominators) to get an overall rate. The studies almost certainly have > different sample sizes and represent different populations. In the > example below, the largest study has the lowest rate and dominates the > pooled estimate. Although you don't mention it, you also need confidence > intervals. > > Here is model code: > *********CODE BEGINS************ > /* Save this as "prop01.do" */ > capture log close > set more off > log using prop01, replace > clear > input study events ntot > 1 60 300 > 2 60 150 > 3 35 100 > 4 20 60 > end > > gen prop = events/ntot > > /* Convert to a full data set */ > gen no_events = ntot - events > save d1, replace > preserve > > keep study events > gen event = 1 > rename events count > tempfile t1 > save `t1' > > restore > keep study no_events > gen event = 0 > rename no_events count > append using `t1' > sort study event > list > > expand count //expand to individual records > save d2, replace > /* Get separate CIs */ > bys study: ci event, binomial agresti > > /* Overall Proportion */ > > /* 1. Pool studies: bad idea > Weights studies by sample size > Incorrect idependence assumption for CI > */ > mean event > ci event, binomial agresti //same > > /* 2. Arithmetic mean of study proportions: > probably best idea*/ > use d1, clear > ci prop > > > /*3. Random Effects Model: assumes normality of study > effects, which must be checked by plots. Don't use > it unless you understand it and do the checks. Here, it > is to the arithmetic mean of the 4 proportions > and I would use just that and its CI > */ > use d2, clear > > xtmelogit event || study: > nlcom invlogit(_b[_cons]) > *****************CODE ENDS******************** > > On Apr 19, 2013, at 12:14 PM, kathryn dennick wrote: > > Hi, > > I am a registered user of STATA and I have a query that I would really like to post in statalist if that's possible at all, please? > > I am currently undertaking a systematic review of cross sectional studies investigating the prevalence of distress in diabetes. The data I have to synthesise is a simple proportion/percentage (those with distress as a proportion of the total diabetes sample). I have to to synthesise this data in a meta-analysis, and I recently attended a course where I learnt about using the metan code from the online STATA journal to conduct meta-analysis of RD, RR and OR data. I'm obviously not able to use this to undertake the meta-analysis as I don't have this type of data. I am know that in entering the data that I have as 2 columns (i.e. as those with depression and then the total sample size), STATA will not read this as a proportion as I need it to. My query is whether you are aware of any STATA command that exists which would enable me to synthesise the data I have and derive an overall proportion/percentage across the studies being reviewed. > * > * 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/ * * 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: Re: "Meta-analysis" of Proportions***From:*Steve Samuels <sjsamuels@gmail.com>

**References**:**[no subject]***From:*kathryn dennick <kath_dennick@hotmail.com>

**st: Re: "Meta-analysis" of Proportions***From:*Steve Samuels <sjsamuels@gmail.com>

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