liesdamned liesand statistics the call anyprob( printed probability of at least births in some month it appears that it is not so unlikely after all that the results reported in the study reflect chance occurrence rather real association between birth month and anorexia one doesn' have to come from texas to fall victim to the texas sharpshooter fallacy what we see here is that the statistical significance of result depends upon the way the experiment was conducted if the aberdeen group had started out with the hypothesis that more anorexics are born in junetheir result would be worth considering but if they started off with the hypothesis that there exists month in which an unusually large proportion of anorexics are borntheir result is not very compelling what next steps might the aberdeen group have taken to test their newfound hypothesisone possibility is to conduct prospective study in prospective studyone starts with set of hypotheses and then gathers data with the potential to either refute or confirm the hypothesis if the group conducted new study and got similar resultsone might be convinced prospective studies can be expensive and time consuming to perform in retrospective studyone has to examine existing data in ways that reduce the likelihood of getting misleading results one common techniqueas discussed in is to split the data into training set and holdout set for examplethey could have chosen / women at random from their data (the training set)and tallied the number of births for each month they could have then compared that to the number of births each month for the remaining women (the holdout set percentages can confuse an investment advisor called client to report that the value of his stock portfolio had risen over the last month he admitted that there had been some ups and downs over the yearbut was pleased to report that the average monthly change was + image the client' surprise when he got his statement for the yearand observed that the value of his portfolio had declined over the year he called his advisorand accused him of being liar "it looks to me,he said"like my portfolio declined by %and you told me that it went up by month " did not,the financial advisor replied" told you that the average monthly change was + when he examined his monthly statementsthe investor realized that he had not been lied tojust misled his portfolio went down by in each month during the first half of the yearand then went up by in each month during the second half of the year when thinking about percentageswe always need to pay attention to the basis on which the percentage is computed in this casethe declines were on higher average basis than the increases