<P> For proper sampling, a process or batch of products should be in reasonable statistical control; inherent random variation is present but variation due to assignable (special) causes is not . Evaluation or testing of a single item does not allow for item - to - item variation and may not represent the batch or process . Replication is needed to account for this variation among items and treatments . </P> <P> As an example, consider a continuous process which produces items . Batches of items are then processed or treated . Finally, tests or measurements are conducted . Several options might be available to obtain ten test values . Some possibilities are: </P> <Ul> <Li> One finished and treated item might be measured repeatedly to obtain ten test results . Only one item was measured so there is no replication . The repeated measurements help identify observational error . </Li> <Li> Ten finished and treated items might be taken from a batch and each measured once . This is not full replication because the ten samples are not random and not representative of the continuous nor batch processing . </Li> <Li> Five items are taken from the continuous process based on sound statistical sampling . These are processed in a batch and tested twice each . This includes replication of initial samples but does not allow for batch - to - batch variation in processing . The repeated tests on each provide some measure and control of testing error . </Li> <Li> Five items are taken from the continuous process based on sound statistical sampling . These are processed in five different batches and tested twice each . This plan includes proper replication of initial samples and also includes batch - to - batch variation . The repeated tests on each provide some measure and control of testing error . </Li> </Ul> <Li> One finished and treated item might be measured repeatedly to obtain ten test results . Only one item was measured so there is no replication . The repeated measurements help identify observational error . </Li>

What is the limitation of this design if only one replicate is obtained