Question

A researcher finds that white bread contains more preservatives and has a higher moisture content than wheat bread. She designs a test to determine whether the type of bread, white or wheat, affects the amount of mold growth. What must be done for the researcher to accurately measure the dependent variable?
She will need to allow mold to grow for more days on the white bread, since it contains more preservatives, to measure the dependent variable.
She will need to limit the dependent variable to white bread or wheat bread.
She will need to allow mold to grow for fewer days on the white bread, since it contains more preservatives, to measure the dependent variable.
She will need to learn how to quantitatively measure mold growth to measure the dependent variable.

Answer 1

She will need to learn how to quantitatively measure mold growth to measure the dependent variable.

Explanation: the dependent variable (amount of mold) must be measured consistently and objectively for both bread types. Examples: percent surface area covered (using a grid or image analysis), number of colonies, dry mass of mold, or fungal coverage scored with a standardized scale. Adjusting growth time differently for each bread would bias the comparison.