15. An experimenter studies vision in low light by having participants sit in a darkened room for either 5, 15, or 25 minutes and then tests their ability to correctly identify 20 objects.

What is the independent variable? Give the levels of the independent variable.

What is the level of measurement of the independent variable?

What is the dependent variable?

What is the level of measurement of the dependent variable?

Would you use the values from the independent variable or the dependent variable to create a frequency distribution?