題組內容

2.[20%] A manufacturer produces steel rods in three sizes (small, medium and large). For the steel rods sold by this manufacturer, 50% are of small size, 40% are of mediu ium size and 10% are of large size. Based on the strength test results, 15% of the small steel rods do not meet the specification. The pe ercentages that do not meet the specification are 10% and 5% for medium and large steel rods, respectively.

(ii) (10%) If a rod randomly chosen from this manufacturer does not meet the specification, what is the probability that this rod is of medium size?