Here are some studies which show clearly the researchers are looking for differences between some or all of the three or more conditions.

As you read them, think about whether the design is independent groups, or repeated measures. Check your answers at the back of the book.

Scarpellini et al. (2008) state that antibodies directed against citrullinated peptides are the most specific serological markers for the diagnosis of rheumatoid arthritis (RA). The authors wanted to determine whether there were significant differences in cyclic citrullinated peptide (CCP) between people with RA, people with osteoarthritis, those with psoriatic arthritis and those with other arthritic conditions. They found that the CCP was significantly higher in RA than in the other conditions.

Button (2008) investigated the possible differences in stressors and health levels between different grades of nurses, i.e. auxiliary nurses, staff nurses, ward sisters, senior nurses and midwives. She found that there was a significant difference in ‘time stress levels’, with ward sisters reporting higher time stress than auxiliary nurses, staff nurses and midwives.

Paterson et al. (2009) wanted to discover whether caffeine would disrupt sleep and also whether two sleep-promoting drugs would reverse the potential disruption. Twelve healthy men participated in a double-blind study where they all received placebo, caffeine, caffeine plus zolpidem and caffeine plus Trazodone.

Gariballa and Forster (2009) carried out a study on the effects of smoking on nutrition status and response to dietary supplements during acute illness. As part of that study, nutrition status was compared between current smokers, ex-smokers and those who never smoked.