Engineers are interested in comparing the mean hydrogen production rates per day for three different heliostat sizes. From the past week's records, the engineers obtained the amount of hydrogen produced per day for each of three heliostat sizes. Then they computed and compared the sample means, which showed that the mean production rate per day increased with the heliostat sizes.
a Identify the type of study described here.
b Discuss the types of inference that can and cannot be drawn from this study.