Question

4.  An hotel chain is testing 4 different laundry detergents to determine how they perform under 3 water temperatures; COLD, MEDIUM, and WARM .  Their linen and other items need to be washed at those 3 different temperatures: COLD, MEDIUM, and WARM. (Some must be washed in Cold water, some in Medium, and others in Warm).

• What design should be used?  Circle the one you would use:

ONE WAY                      TWO WAYS Block               TWO WAYS with Interaction, (Factorial)

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Answer 1

TWO WAYS with Interaction design should be used for this study.

Here, two variables, detergent that are 4 different laundry types and the other variable water temperatures that are COLD, MEDIUM, and WARM.

An interaction effect is a change in the simple main effect of one variable over levels of the second. The interaction between Laundry types and Water temperature is a change in the simple main effect of Water temperatures over levels of Laundry types or the change in the simple main effect of Laundry types over levels of Water temperatures. In either case the cell means cannot be modeled simply by knowing the size of the main effects. An additional set of parameters must be used to explain the differences between the cell means. This is called an interaction.