How is questionnaires invalid?

Questionnaires can be invalid due to several factors, such as poorly designed questions that lead to ambiguity or bias, which can result in unclear or misleading responses. Additionally, if the sample population does not accurately represent the target group, the findings may not be generalizable. Responses can also be influenced by social desirability bias, where participants answer in a way they think is more acceptable rather than their true feelings. Lastly, low response rates can undermine the validity, as non-respondents may differ significantly from those who do respond.