For the following example, think about the following:
• How was the outcome measured?
• At what level was the outcome measured?
What was the control group?
• Were confounding variables controlled?
A study was performed to investigate the factors involved in motion sickness in travellers. Fifty passengers on a very rough ferry crossing from Dover to Calais acted as participants. Half of the participants had a large greasy breakfast before the ship left the harbour, and half did not. A record was kept Of the amount of vomit produced by each participant, in milliliters.