Four samples are taken and averaged every hour from a production line and the hourly measurement of a particular impurity is recorded. Approximately one out of six of these averages exceed 1.5% when...

Four samples are taken and averaged every hour from a production line and the hourly measurement of a particular impurity is recorded. Approximately one out of six of these averages exceed 1.5% when the mean value is approximately 1.4%. State assumptions that would enable you to determine the proportion of the individual reading exceeding 1.6%. Make the assumptions and do the calculations. Are these assumptions likely to be true ? If not, how might they be violated ?