The article “evaluating tunnel kiln perfor-mance” (amer. ceramic soc. bull., aug. 1997: 59–63) gave the following summary informationfor fracture strengths (mpa) of n=169 ceramicbars fired in a particular kiln: x=89: 10; s=3: 73.a. calculate a (two-sided) confidence intervalfor true average fracture strength using a con-fidence level of 95%. does it appear that trueaverage fracture strength has been preciselyestimated? b. suppose the investigators had believed apriori that the population standard deviationwas about 4 mpa. based on this supposition, how large a sample would have been requiredto estimatemto within .5 mpa with 95%confidence?