A student performed an experiment to see if water temperature affects the level of activity

in aquatic snails. The student set up four tanks with five snails in each tank. All four of the

setups were identical in every way, except for the temperature of the water. In order to

make the conclusions more valid, the student could

A.

alter the pH of the water

B.

change the size of the tank

C.

carry out the experiment for a shorter period of time

D.

use a larger number of snails

D

Explanation:

A is not viable as altering the Ph would affect the snails, and would not focus on how temperature affects the snails

B Expanding the tank would indeed give the snails more room to move around in, but in questions like these, you need to choose the best fit for the question. The larger tank also wouldn't really make the conclusion more valid

C Carrying out the experiment for a shorter length of time would only decrease the amount of data you would get to analyse to determine whether there was an impact on the snails

D Using a larger number of snails would indeed make the conclusion more valid. This is because the number of snails that are tested increases the validity of a claim of a trend. If 10 snails instead of 5 snails are more active in warmer water, the validity of the claim is higher and more believable.