Question

In a between-subjects experiment examining the effects of plate size on amount of food eaten, the amount eaten by one group of participants is measured after eating food on 12 inch plates. Some time late, the amount eaten by the same group of participants is measured after eating food on 10 inch plates. What are the two disadvantages of the design and what two specific methods will help in correcting the disadvantages associated with the new between subject design

Answer 1

The disadvantage is as follows:

• The same group of participants are eating the food on the 12-inch and 10-inch plates. Thus, this is not, strictly speaking, a between groups design.
• The researcher has not standardized the treatment conditions. For instance, during different time slots of the same day, participants are served food. There is bound to be carryover effects due to this.

The following methods to correct the aforementioned disadvantages are suggested:

• Introduce a separate group of participants who would be exposed to the 10-inch plates condition. These group of participants should be matched with the 12-inch plates group.
• Establish standardized conditions while presenting the food i.e., ensure they are served the same "type" of food during the same time of day. Another import consideration is to ensure that no meal is consumed before the presentation of the food both groups.