Coffee drinkers often claim that the caffeine in the coffee makes them more alert. A researcher wonders if this enhanced alertness is merely an illusion or if caffeine actually makes people more alert. To test the effect of caffeine on alertness, the researcher asks people to drink one cup of caffeinated coffee, one cup of plain water, one cup of caffeinated water, or one cup of decaffeinated coffee. After drinking the beverage each participant was given an electroencephalogram (EEG). The researcher hypothesized that the caffeinated beverages would result in greater electrical activity than the non-caffeinated beverages. Which of the following would be most likely to increase the size of the treatment effect in this study? a. Only use people in the study who are between the ages of 25 and 35 rather than 25 and 75.
b. Increase the amount of beverage participants drink from one cup to two cups.
c. Have experienced EEG technicians collect data rather than train students to administer an EEG.
d. Including as many different types of people as possible in the study (i. e., men and women, people from different regions of the country, etc.)