When comparing stimuli, letters of the alphabet are typically chosen to label the items. However, if the letters are not chosen carefully, you run the risk of biasing preferences. Included below are a few points to ensure you have labeled your concepts/products/stimuli with the least chance of bias.
- Don’t use letters that can be placed in alphabetical order (e.g., A, B, C or K, L, M). Instead mix them up so that there is no impression that one product should be ranked first.
- Make sure your letters do not match the product names or attributes. Assign your labels so there is no chance the participant could associate a letter with an item being compared.
- Keep in mind that letters at the beginning of the alphabet are considered more favorable than those at the end. Additionally, certain letters should not be used to label stimuli. Specifically those viewed unfavorably include Q, U, V, X, Z or F.
- Ensure the letters you choose do not sound similar (e.g., D, B & G or N & M). When discussing stimuli it may not always be clear which item a participant is referring to if the concept labels sound the same
- Finally, be sure the letters you have chosen cannot be arranged to spell a word, especially an inappropriate one.
The best part of choosing labels for stimulus testing is that there are ways you can use the bias-causing letters to your advantage. For example, if a product is continually getting a low rating and you want to ensure this assessment is correct, try assigning it the letter “A” in the next group to see if participants still don’t like it. Or, conversely, if a product is continually surfacing as a favorite, use an unfavorable label like “F” or “X” and test if it still comes out on top.
Hardwick Research has been conducting market research in the Seattle, WA. We have been having fun choosing labels for stimulus testing for over 20 years. If you are interested in working with us or receiving a proposal, please call 206-232-9400 or email us through our Contact page.