The 90% confidence interval for the true mean of national statistics examinationscores is 81

The 90% confidence interval for the true mean of national statistics examinationscores is 81 <>< 87.="" assume="" that="" the="" population="" standard="" deviation="" was="" notknown="" and="">< 30.i)="" find="" the="" standard="" deviation="" of="" the="" sample="" mean="" for="" the="" data="" used="" to="" obtainthe="" confidence="" interval.ii)="" construct="" and="" interpret="" the="" 95%="" confidence="" interval="" for="" the="" true="" mean="" ofnational="" statistics="" examination="">