Comparison Study by Paired Means Difference

The paper is intended to be used as a research methodology guideline for comparison studies using T and Z tests. Comparison studies may occur in the context of quality control management. Within a production batch, one can divide the batch into two parts, treating them as sample 1 and sample 2 respectively. A comparison study of these two samples would tell us whether the production has consistent quality. If there is a consistent quality in the batch, the difference of the means of the two samples would not be significant. Throughout the discussion in this paper, the confidence interval is fixed at 95%.