Question

a researcher wanted to determine the effect water temperature has on goldfish respirations. the researcher placed the goldfish in three different bowls of water with three different temperatures and counted the goldfishs respirations for two minutes in each setting. what factors must be kept constant to obtain valid results?
○ length of time, size of tank, volume of water
○ number of respirations, volume of water, the goldfish
○ water temperature, length of time, volume of water
○ the goldfish, size of tank, water temperature

Explanation:

In an experiment, the independent variable is water temperature (tested), and dependent is respiration rate. Controlled variables (kept constant) should not affect the outcome. Let's analyze options:

• Option 1: Length of time (already set to 2 mins, should stay constant), size of tank (affects environment), volume of water (affects space) – these are controlled variables.
• Option 2: Number of respirations is the dependent variable (measured, not controlled), so invalid.
• Option 3: Water temperature is the independent variable (varied, not controlled), so invalid.
• Option 4: Water temperature is independent (varied), so invalid.

So the correct factors to keep constant are length of time, size of tank, volume of water.

Answer:

A. length of time, size of tank, volume of water