Two students completed an experiment to determine if pesticide use at local farms was causing fish kills in a local pond. The steps of the experiment are listed below. Select one location to collect water samples in the pond. Collect a 5-mL water sample at 8 am for two days. Measure the amount of pesticide present in each sample using the same measurement tools. After analyzing their data, the students conclude that pesticide runoff from farms is not causing the fish to die in the pond. Which of these statements best describes why their conclusion is not reliable? The pesticide measurements were the dependent variable. The samples were collected at different times. The samples were only collected for two days. The time of sample collection was not an independent variable.

The pesticide measurements were the dependent variable

Explanation:

According to this question, an experiment to determine if pesticide used at local farms was causing fish kills in a local pond was conducted by two students. They followed the following steps:

- Select one location to collect water samples in the pond.

- Collect a 5-mL water sample at 8 am for two days.

- Measure the amount of pesticide present in each sample using the same measurement tools

However, after analyzing the data, they concluded that "runoff from farms is not causing the fish to die in the pond". The students' conclusion is not reliable because THE PESTICIDE MEASUREMENTS WERE THE DEPENDENT VARIABLE.

Note that, the dependent variable in an experiment is the measured variable while the independent variable is the manipulated variable. In this case, the students ought to measure the death RATE OF FISH KILLS as the dependent variable instead. The PESTICIDE is the independent variable of the experiment not dependent variable. This was the reason for the unreliability of the conclusion.