Summary of #PHTwitJC 27: ‘Greening vacant lots to reduce violent crime: a randomised controlled trial’

But on Wednesday 31st July, #PHTwitJC discussed:

GARVIN E, Cannuscio C, Branas C. (2013) Greening vacant lots to decrease violent crime: a randomised controlled trial. Inj Prev 19:198-203 doi:10.1136/injuryprev-2012-040439.

The full text may be accessed at this web link:


The discussion was organised around the five questions at the preceding newspaper post post.

1. Were the goals of this study clear? (consider whether it clearly defined the population, intervention, outcome and comparison)

The participants believed that the aims of the paper were clear and justified with a solid introduction department.

A few words used in the newspaper were new to participants – possibly on account of the analysis using US phrases – but they were either well described in the paper or were readily understandable.

“I thought that the aims were clear too – ‘greening’ was new to me nicely recognized ” – @duncautumnstore

“The vocabulary felt very American – would people call them’lots’ at UK? What would we say instead? ” – @carotomes

2. Was the methodology right?

Randomised controlled trials (RCT) are one of the most powerful research designs, and it had been agreed it was an suitable approach here.

“RCT was appropriate to assess causality involving greening and crime, but unsure whether truly randomised…” – @carotomes

Participants mentioned that there was some ambiguity regarding the randomisation procedure, and it had been hard to pick out from the paper how many clusters of plenty were ultimately randomised.

“E.g. P199 each bunch lot was seen by PHS to ascertain whether appropriate to ship for greening authorisation? I didn’t fully comprehend that this – seemed as a vetting procedure prior to randomisation, also uncertain of randomisation procedure. ” – @carotomes

“yes, it was a little unclear. I couldn’t work out how many clusters have been randomised in the conclusion ” – @duncautumnstore

There was some debate about if the procedure used to group lots supposed that the layout has been nearer to a bunch RCT. It had been noted this would nevertheless be a powerful layout, but that also more information ought to be provided when running a cluster RCT.

“I believed that. Or if it was closer in design to cluster-RCT” – @duncautumnstore

“absolutely – it had been a cluster RCT rather than RCT. But no talk of heterogeneity assessment” – @carotomes

Several of the issues of running an RCT to a constructed surroundings intervention were also mentioned, since these might account for a few of the compromises in research made.

“not often you have the circumstances to do an RCT about the constructed environment, so perhaps some compromises had to be made. ” – @duncautumnstore 

“[Pennsylvania is] large enough to fit a few more clusters into the trial… maybe financial reasons, but we still all don’t know from the paper” – @duncautumnstore

3. Can the analysis utilize suitable procedures?

There was a discussion over the difference-in-differences method utilized, and whether any other statistical methods could have been used rather than

Participants found the difference-in-differences procedure intuitive, however, in the expertise of these participants it infrequently appeared in data text books. This made it harder to judge exactly what the advantages and constraints are of utilizing difference-in differences within this newspaper.

“that I ’d never encounter difference-in-differences before. Not sure on its strengths and the appropriate circumstances to utilize it. ” – @duncautumnstore

4. Can you believe the results? The study reports non-significant reductions in crime and progress in perceptions of disease, but also a significant advancement in residents perceptions of safety, what could explain the findings?

The participants spoke that reductions in crime from green distances seemed plausible, but since there was some uncertainty within the methodology employed in this research it was hard to be confident about a few aspects of the results.

“I really don’t know if I can be confident as I’m unclear in their strategy and analysis” – @carotomes

The authors also highlighted the preliminary character of these consequences in the newspaper, and facets of this were discussed with the participants. 

“I get the feeling that the authors were a Small tentitive from drawing too many certain conclusions also ” – @duncautumnstore

“[the] authors themselves recognise the constraints of sample and unrobust information ” – @carotomes

“they use phrases like ‘preliminary proof ’ and advocated larger trials” – @duncautumnstore

The participants identified the potential for bias in the way in which the questionnaire was used to measure the resident’s perceptions of safety.

“questionnaire on perceptions of security and violence primes interviewees of research purpose! ” – @carotomes

5. What implications do the findings have for public health practice & practice?

The talk of these consequences referred back to the tentative nature of the findings. It was suggested that the focal point of this newspaper might have been around the viability of this method rather than the results.

“feels like concentrate on newspaper should’ve been’is that this method practical to test Q’ in preparation of bigger investigation ” – @carotomes

Research findings are essential for advocating for good general health, but a participant felt that the results from this newspaper weren’t striking enough to aid advocate for green spaces.

“an Essential methods newspaper, but that I don’t believe that the results are striking enough to be the one employed to advocate for green distances ” – @duncautumnstore

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