Conduct multiple trials to test a prediction and draw conclusions about the relationships between predictions and results.

Scientists would generally interpret the phrase “multiple trials” as meaning to repeat the same experiment in the identical way many times. This repetition is necessary to determine how accurate our experimental set-up is and our way of making and recording our observations. If our procedures are scientifically sound, we should get approximately the same answer every time. Of course, there will be some variation each time, but the amount of variation will be fairly small.

If the amount of variation is large and unpredictable, there is something we have not considered in the way we have set up the experiment, made our observations, or recorded the information. Often this is because of a mistake that we are making but are not aware of. Sometimes it is because there is something influencing our experiment that we do not know about and that we have not controlled. As scientists, we then try to determine what is causing the lack of reproducibility. Some important scientific discoveries have been made when experiments did not work “correctly,” and scientists had to then figure out what was really going on.

The way this standard is written, the phrase “multiple trials” can mean reproducing the same exact experiment. However, it can also mean making a specific kind of measurement or observation multiples times under slightly different conditions. Scientists often vary one condition at a time to see what effect that change has on a situation. Thus, they conduct multiple trials that are not exact repetitions in order to test a prediction.

In a class, you often have both kinds of multiple trials happening. For example many groups in a class may be testing the effect of salt water compared with fresh water on the growth of plants. They are all measuring plant heights under different conditions of watering. Each group is doing multiple trials by measuring plant height with different saltiness of water. This is the multiple trials with some controlled variation.

Assuming all groups are following the same procedure, you can compare across groups to determine how reproducible the results are. This is doing multiple trials that are repetitions. By comparing the results across the groups, you can get a measure of the reproducibility of the experiment and the range of values reported for the same conditions.