Question

A student would like to do an experiment to see how light can affect the growth of a plant. The student looks up two different lab procedures on the internet and would like to combine the procedures to make a better set of procedures. Read the table below to compare both lab procedures that the student found online.

Step Procedure A Procedure B
1 Plant 1 soybean in two identical pots with the same amount of soil and label them “Plant 1” and “Plant 2” Using two identical pots filled with the same amount of soil, plant 1 soybean in a pot and label it “Plant 1” and plant 1 tomato seed in a pot and label it “Plant 2”
2 Add water to “Plant 1” every other day Add the same amount of water to both plants every 3 days
3 Place both pots in a sunny window Place Plant 1 in a sunny window and place Plant 2 in an area with less than 2 hours of sunlight each day
4 Use a ruler to measure both plants each day Use estimation to see which plant grows more each day
5 Record your results in your notebook Record your results in your notebook
6 Continue measuring for 35 days Continue measuring for 35 days


What is the best procedure for step 2?
Responses
A Add water to “Plant 1” every other dayAdd water to “Plant 1” every other day
B Place both pots in a sunny windowPlace both pots in a sunny window
C Using two identical pots filled with the same amount of soil, plant 1 soybean in a pot and label it “Plant 1” and plant 1 tomato seed in a pot and label it “Plant 2”Using two identical pots filled with the same amount of soil, plant 1 soybean in a pot and label it “Plant 1” and plant 1 tomato seed in a pot and label it “Plant 2”
D Add the same amount of water to both plants every 3 daysAdd the same amount of water to both plants every 3 days

Answer 1

D

Both plants should get the same amount of water on the same schedule so watering is not a confounding variable when testing the effect of light.