A Researcher Wanted to Determine If the Presence of Blue

Multiple Choice

A researcher wanted to determine if the presence of blue light, such as that emitted from a cell phone, interrupted sleep. Participants were asked either to sleep with their cell phone nearby or to sleep with their cell phone in another room. A device recorded their sleep cycles for one week. Results showed sleep quality was poorer in the cell phone present group. What design change needs to be made to rule out alterative explanations for the result?

A) use a within-subjects design rather than a between-subjects design.
B) measure sleep quality for longer than one week.
C) add a condition where blue light is emitted from a device other than a cell phone.
D) Any of the above can rule out alternative explanations