Question

mai wants to grow corn on the farm she just bought. the previous farmer grew corn for several decades and kept detailed records of his crop production each year. these records include the amount of sunlight, the amount of rain, the average yield, and other such figures. in an effort to help mai out, the previous farmer compares his records of using two popular fertilizers: plantx and earthy. he pulls his records for the 7 seasons he used earthy on his corn. he uses these records to compare the average corn yield for the 7 seasons that he used earthy. if applicable, he will recommend the better fertilizer to mai. (a) first choose whether the procedure described above is an observational study or a designed experiment. then further categorize the procedure by choosing the correct type of observational study or designed experiment. observational study: prospective, retrospective; designed experiment: double - blind, completely randomized. (b) which one of the following best describes the explanatory (independent) and response (dependent) variables? the explanatory variable is the brand of fertilizer and the response variable is the average corn yield. the explanatory variable is the brand of fertilizer and the response variable is the sunlight. the explanatory variable is the average corn yield and the response variable is the brand of fertilizer. the explanatory variable is the sunlight and the response variable is the average corn yield.

Explanation:

(a) The farmer is looking at past records, so it is a retrospective observational study. He is not imposing any treatment, just observing and comparing existing data.
(b) The brand of fertilizer is what the farmer is manipulating (or could manipulate in a future study), so it is the explanatory variable. The average corn - yield is what is being measured as a result of the fertilizer use, so it is the response variable.

Answer:

(a) retrospective
(b) The explanatory variable is the brand of fertilizer and the response variable is the average corn yield.