Question

the passage below describes an experiment. read the passage and then follow the instructions. dr. roth was the land - manager for a prairie that had become overrun by unwanted grasses. these grasses crowded out other plants. dr. roth thought that she could use fire to remove the unwanted grasses and allow other plants to grow. but she didnt know how often the prairie should be burned. dr. roth marked off six plots within a large area of the prairie. she used carefully controlled fires to burn all of the plants in each plot. she burned three of the plots once a year for three years. she burned the other three plots twice a year for three years. a year after the last fire, dr. roth counted the number of unwanted grasses in each of the six plots. complete the sentence. in this experiment, the number of times the plots were burned each year was ____ a dependent variable an independent variable

Explanation:

In an experiment, the independent variable is what the researcher manipulates. Here, Dr. Roth decides how many times (once or twice) to burn the plots each year. The number of unwanted grasses (the dependent variable) is expected to change based on the burning - frequency. So the number of times the plots were burned each year is controlled by the researcher and influences the outcome variable.

Answer:

an independent variable