Management Science and Jury Size: A Commentary

The analogy of a jury decision is a common one when discussing the Management Science application of quality control. An incoming lot is “innocent” until proven “guilty” by inspection. There are costs for “convicting” a good lot and there are costs for “acquitting” a bad lot. Military standard acceptance sampling tables even allow us the option of using more discriminating sampling plans when the cost of making errors by too frequent “conviction” is high, relative to the converse situation.The general concern of the article is to estimate the impact of reducing jury size from the traditional number of twelve jurors. Some important factors are that in 64.2% of cases with 12 jurors, there is a unanimous vote to convict. Similarly, in 30.3% of these cases there is a unanimous vote to acquit. If jury sizes are reduced, it seems unlikely that any unanimous 12-person jury decision would change. That is, arguments were presented in a trial to convince all 12 jurors to have the same opinion. By reducing the jury size during that trial, there seems to be no reason to expect that remaining jurors would reverse their opinion, with all other things being the same.