Three laboratory technicians, calling them X, Y and Z, make determinations of an unknown concentration . One can assume that their observations are independent and N (, 2). From their measured value series, they calculate x , s_x, y , s_y respectively z , s_z,

(a) X, which knows its basic course in statistics, has calculated x = 16.3 and sx = 0.88 based on 8 measured values. She gives a correct interval estimate of with a confidence level of 95%. Do you agree?

(b) Y and Z, both of which unfortunately have given the aforementioned course a rather distracted interest, blaspheme that y s_y and z s_z are interval estimates of with a confidence level of at least 95%. Y has done 5 measurements and Z has done 10. Are any of them right?