Question

Explain the difference between single sampling plan and double sampling plan.​

Answer 1

Single Sampling Plan:

Here, a single sample of size n is drawn from a lot of size N, and the lot is accepted if the number of defectives in the lot (d) is less than the specification (c) i.e.

A sample of size n is drawn and the items of the sample are inspected. Let the number of defectives in the sample be d. If.

• d < c, the lot is accepted and the defective items i.e. d are replaced.
• d> c, the lot is rejected and then the entire lot is inspected and the defective items are replaced.

It is evident that single sampling plan is simple to understand and easy to execute. Moreover, the information from each sample can be represented by a control chart.

Double Sampling Plan:

This type of scheme is more economical than single sampling scheme when the quality of incoming goods is high. Here sample is drawn in two stages. The second sample is drawn only when clear cut decision cannot be drawn from the first sample. Let c1 and c2 be the specified defectives in first and second samples respectively.

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