7. 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 exceeds 1.5% when the mean value is approximately 1.4%. State assumptions that would enable you to determine the proportion of the individual readings exceeding 1.6%. Make the assump- tions and do the calculations. Are these assumptions likely to be true? If not, how might they be violated?