In situations where testing is destructive or very expensive, small sample plans such as the chain sampling plan are used. The original chain sampling plan introduced by Dodge, known as the ChSP-1 plan, calls for the use of past lot inspection results when the current sample has a nonconforming unit. This selective use of related lot inspection results helps to achieve a more discriminating Operating Characteristic curve but it does not lead to a reduction in sample size. This paper therefore proposes a modified chain sampling plan which always utilizes the past lot inspection results in order to achieve very small sample sizes. The performance of the proposed modified chain sampling plan, designated as the MChSP-1 plan is then evaluated by comparing it with the ChSP-1 plan. The paper also addresses the question of how the performance of MChSP-1 plan will be affected in the presence of trend in incoming quality of the lots. The new plan will be particularly useful in situations warranting small sample sizes.
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