DCluster questions
Thanks for the reply Virgilio,
2) Will opgam/kn.iscluster only detect "hotspots" or will they also detect "coldspots" i.e. areas of statistically unlikely lower incidence rates ?
You get a p-value, so you could take the areas with very large p-values as cold-spots. But detection of cold-spots is not of interest, is it?
Um I'm new to this field so I'm probably missing something but - why wouldn't it be interesting? It might tell me about local protective factors, or localized case ascertainment holes I would imagine ? Anyhow I have something in mind to do it - although its low down on my todo list for now.
4) How do I decide what the correct value for fractpop is ? I initially had it set to .25 and I was getting cluster of 50% of my cases which made no sense.
You may try different values of fractpop if you want to detect smaller clusters.
Ok...but that feels kind of arbitrary to me. Is there a logic by which to select a size ?
5) Is there any correction for multiple testing in the opgam() command ? I have over 3000 areas - do I need to set a very low alpha ?
For the Spatial Scan Statistic you should only pay attention to the significance of the most likely cluster, as this is what Kulldorff's test is testing for. But you can use the p-value reported for the other secondary clusters as a guidance.
For GAM, you probably want to make a multiple test correction. Another good option is to plot the centres of the clusters detected as this will give you and idea of the areas with significant high risk.
This reply confuses me - if I['m using the Kuldorff's scan stat inside the GAM - then I don't need to worry about multiple comparison or I do ?
Hope this helps.
Virgilio
Yes - quite helpful and much appreciated. Thank you! James