Production management principles and practices

Production Management

Systematic Sampling or Interval Sampling:

Tuff Tire should undertake Random Sampling of its tires in each of its production facilities as normally in testing quality of production cycles, random sampling is used. In case of a random sampling, all the items stand an equal chance of selection which can be calculated. Random sampling mechanism guarantees that bias is removed regarding inclusion in the survey. Out of the five common random sampling viz. simple random sampling, systematic sampling, stratified sampling, cluster sampling, and multistage sampling, systematic sampling, which is also known as interval sampling, should be used. Interval sampling indicates that a gap or interval between each selection. This method is frequently used in the industry, wherein an item is selected for testing from a production line to make sure that the items coming out of the production line is working to specification.

It is upon the Production Manager to select say every 20th tire on a production line to test for flaws and adherence to quality. This procedure needs the first item to be selected at random and as a starting point and subsequently every 20th tire is chosen for testing. At this point it is necessary for selection of a fixed sample size. In the present case, it is first essential to know the whole population size wherefrom the sample is being drawn. The appropriate sampling interval, I is subsequently calculated by dividing the population size, N, by the required sample size, n, by the formula I = N/n. In our example, say, we are to take a systematic sample of 500 tires with a sample size of 10,000 tires which is manufactured every week, the sampling interval will come to be I = N/n which is 10000/500 = 20.

It should be noted that where 'I' is not a whole number, then it is rounded off to the nearest whole number. The tires will be assigned sequential numbers. The starting point will be chosen through selection of a random number between 1 and 20. Supposing this number is 9. Then the 9th tire on the total population of tires would be selected along with every subsequent 20th tire. The sample of tires would thus be those corresponding to the tire numbers like 9, 29, 49, 69, 89, and 109 and so on till 9929, 9949, 9969 and 9989. The merit of systematic sampling is that it is easier to choose one random number and thereafter every Ith item i.e. 20th in our case compared to selecting as many as random numbers as the sample size. Besides, it also gives a good spread throughout the population size. However, a demerit is that a list is needed to begin which, in case it is desired to know the sample size and calculate the sampling interval. (Sampling Methods)

Other Quality Control (QC) Measures:

Tuff Tires should also follow the Quality Cost Delivery -- QDC approach to measure efficiency. Through the use of QDC there can be a focus to clarify the priorities for enhancing the production processed or service delivery. Simplicity gives a big picture, simplification of a complex production process and identification of unambiguous path for improvements. Feedback can also be used to measure the results of any changes that have been made to the production process or service delivery. QCD gives quick feedback -- it delivers the facts and figures required to arrive at meaningful decisions.

Another aspect is benchmarking, wherein QCD helps how well the business is presently performing to assist one to decide which component of the business or production process to improve. The data supplies a standard to set targets for the future. Once the company arrives at a decision regarding which activities to improve, it is required to review them, to establish why certain practices are performed in a particular manner.