Example Experiment Assessment

What do you think of Alisha's microwaved water experiment?

Some suggested changes:

1. Alisha should probably mix up her treatments in a random way instead of having them in neat rows.

water-experiment-randomized


Why? Because it is possible that  the right side of the table is colder or gets less light than the left. That means the plants in that treatment are not going to grow as well, but for reasons other than the treatment. Randomizing the plant treatments helps reduce the impact of those kinds of environmental variables.

2. Alisha should consider setting up an automatic watering system or have a friend apply a measured amount of water using a number or letter system to disguise the treatments. This is called a "blind" experiment.

Why? Because Alisha might be unconsciously biased and apply less water to one of the treatments without realizing it. If Alisha's friend doesn't know what results she is expecting, he or she is less likely to try to manipulate the results.

Do you have any other suggestions for changes? Send an e-mail to growingwithscience@gmail.com.

© Roberta Gibson 2015