late last month, Jim Runnels,a sales representative for the paint Tint Corporation, was called to the plant of Townhouse Paint Company, one of his largest account. The purchasing agent for Townhouse Paint was complaining that the tube of paint tint it had received over the last couple of weeks were not within the specified range of 4.9 to 5.1 ounces
The off-weight tubes had not been detected by Townhouse's receiving clerks and had not been or otherwise checked by their quality control staff. The problem arose when Townhouse began to use the tinting agent and found that the paint colors were not matching the specification. The mixing charts used by the salespeople in townhouse's retail stores were based on 5-ounce tubes of tinting agent.
In consequence,Townhouse had to issue special instruction to all of its retail people that would allow them to compensate for the off-weight tubes. The townhouse purchasing agent it clear that a new supplier would be sought if this problem recurred. Paint Tint's quality control department was immediately summoned to assist in determing the cause of the problem.
Paint Tint's quality manager, Ronald Wilson, speculated that the cause of the problem was with the second shift. To analyze the problem, he entered into a spreadsheet the data from all the previous samples taken over the last two months. As it turned out, 15 random samples had been taken over the two - month period for both the frist and the second shifts. samples always consisted of 10 randomly selected tubes of paint tint. Also, separate sampling schedules were used for the first and second shift would not automatically assume that it would be subject to a random sample just because the first shift had been earlier in the day.
After entering the sample weight data of the tubes into the following spreadsheet and calculating the sample means. Ronald was quite puzzled. There did not seem to be any noticeable difference in the average weights across the two shifts. Furthermore, although the lines were running at less than full capacity during the first six samples, there still did not seem to be any change in either line after reaching full production.