Nested ANOVA model applied to evaluate variability of ready-mixed concrete production

The ‘‘between-batch’’ variance represents the variability between production units and is due to variations of the properties of raw materials, batching and mixing process, slump adjustment, weather conditions, etc. It also includes the same factors affecting ‘‘within-batch’’ variance. The ‘‘within-batch’’ variance represents the variability inside the batch. The variability between samples taken from de same batch is affected mainly by the loading and mixing processes (mixing time, mixer rotation speed, loading materials sequence, etc.). The ‘‘within-test’’ variance represents the variability of the measurements; in this case, the variation between strength tests results of concrete specimens of the same sample.