在准备CRE考试，想开辟一个专区，把自己平时遇到的问题，分享出来，请论坛前辈不吝赐教。
如果有会做的，不光请给出结论，最重要的是给出解答过程。感谢！共同进步
今天给出问题是：
该试题来自于CRE题库，对应的是章节是CREHandbook[color=Red]part2：ProbabilityandStatistics
forReliability
1.AnMBAclassprojectrequiresyourteamtoestimatetheproportionofpeoplethatwillvoteinthenextelection.Youhavenopriorknowledgeofhowmanyareexpectedtovote.Inordertoassureanestimatethatfallswithinfivepercentagepointsoferror,howmanypeopledoyouandyourteamhavetosurveytoachievethisestimatewith95%confidence(assumeNormalapproximationapplies)?
385people
271people
73people
aminimumof30peopleisrecommended
2.Ifthecorrelationbetweenafactorandaresponseinasimplelinearregressionanalysisisestimatedtober=-0.90,thenthepercentofvariationintheresponsethatisattributableto(explainedby)thefactorunderstudyis:
81%
90%
10%
19%
