When page four of the study tells us that "CCTV had no statistically significant effect on arrest rates ..." we learn that the study failed. Perhaps CCTV reduc

When page four of the study tells us that "CCTV had no statistically significant effect on arrest rates ..." we learn that the study failed. Perhaps CCTV reduced arrest rates. Perhaps CCTV didn't reduce arrest rates. The lack of statistical significance means that the people doing the study failed to find out which it was. Notice that if CCTV is super-duper effective, then it should be fairly easy to get a statistically significant result. This is well known; so the executive summary on page four is an example of weasel-wording. The authors insinuate that CCTV wasn't super-duper effective, heck, it didn't do much of anything. But they weasel out of talking about the power of the study. If you don't expect CCTV to be super-duper effective, you might still be interested in whether it was a little bit effective. CCTV can be a lot cheaper than foot patrols. It might be disappointing, yet still earn its keep. We return to the question of the statistical power of the study. A powerful study, that fails to get a statistically significant result, puts a tight upper bound on the usefulness of CCTV. If that is less than what CCTV cost we know to spend our money on something else. A weak study puts a slack upper bound on the usefulness of CCTV. If it fails to get a statistically significant result, then we learn that CCTV isn't super-duper effective, but since neither pro- nor anti- were claiming that, their quarrel continues as before. I'm giving up, having skimmed to page 15 of the PDF, because, well you can read page 15 yourself and see why I think that it reveals the authors to be completely clueless about statistics.