The strength of concrete used in commercial construction tends to vary from one batch to another. Consequently, small test cylinders of concrete sampled from a batch are "cured" for periods up to about 28 days in temperature and moisture-controlled environments before strength measurements are made. Concrete is then "bought and sold on the basis of strength test cylinders" (ASTM C 31 Standard Test Method for Making and Curing Concrete Test Specimens in the Field). The accompanying data resulted from an experiment carried out to compare three different curing methods with respect to compressive strength (MPa). Analyze this data.

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Batch Method A Method B Method C 30.7 29.1 30.0 31.9 30.5 26.9 28.2 32.4 26.6 28.6 33.7 30.6 32.2 34.6 33.0 29.3 28.4 32.4 29.5 29.4 30.5 32.6 30.5 33.5 32.4 27.8 30.7 33.6 29.2 33.2 4 8 10