Answer:
Initial age of ghost shrimp and water temperature
Step-by-step explanation:
In an experiment, there are several variables (alterable factors) that determine the outcome of the experiment. A CONTROLLED variable or CONSTANT is a variable that is kept constant or unchanged throughout the experiment. The constant is not changed because it can affect the other variables (outcome) of the experiment.
For this experiment conducted by Mary Beth on the effect of size of the tank on the size of the shrimp after 6months, the constants are INITIAL AGE OF GHOST SHRIMP and WATER TEMPERATURE. This is so because the ghost shrimps of the same initial age must be used to start the experiment, so as to be able to measure the actual effect on the growth. Also, the water in the respective tanks must be the same Temperature so that one experimental group will not be favored over another.