Aziza is designing an experiment to test whether the color of a hummingbird feeder affects the number of hummingbirds that feed at it.
She plans to buy four hummingbird feeders and four different colors of paint. She will paint each feeder a different color, fill each feeder
with hummingbird food, and then hang the feeders outside so that she can count how many hummingbirds visit each feeder.
Which of the following factors should Aziza keep constant throughout her experiment in order for her experiment to be reliable and fair?
the shape of the
hummingbird feeders
the color of the
hummingbird feeders
the size of the
hummingbird feeders
the height at which the
hummingbird feeders are hung
the number of hummingbirds
that visit each feeder
the kind of hummingbird food
placed in each feeder