Table 1.

Strategies to ensure sample validity in Web research

Strategy category	Specific techniques
Procedural/design	• Limit access to Web‐based data collection sites. (PEDI)
	• Require potential respondents to answer questions that demonstrate “insider knowledge”. (PEDI, VC)
	• Ask potential participants to report how and where they found out about the research study and provide actual links to these Web pages. (PEDI)
	• Do not advertise the amount or type of compensation that will be provided to study participants. (VC)
	• Collect the same information at multiple points and then examine for consistency. (PEDI)
	• Develop a plan to re‐contact potentially suspicious respondents as part of the research protocol prior to data collection. (PEDI, VC)
Technical/software strategies	• Track the Internet Protocol (IP) address of individual respondents to identify potential multiple enrollees. (VC)
	• Gather date and time stamps for Web‐based responses to identify respondents completing surveys more quickly than expected. (PEDI, VC)
	• Use software created to reduce risk of attacks from programs written to automatically populate surveys. (e.g., CAPTCHA)
	• Restrict enrollment to respondents who enter a Web data collection site through approved Web links (URLs). (VC)
Data analytic strategies	• Identify pairs of items that can be examined together to evaluate the logic of an individual participant's responses. (PEDI, VC)
	• Analyze the extent to which responses are in keeping with previous research with the target population. (PEDI, VC)
	• Analyze the extent to which responses from participants suspected of misrepresenting eligibility differ from the remaining study sample (sensitivity analysis).

Note: PEDI, PEDI‐CAT‐ASD web‐based study; VC, VetChange web‐based study.