Again, there is no perfect answer to this question. Every website is different and will have a different “sweet spot”; a rate high enough to secure the desired sample, but low enough to avoid respondent fatigue. We suggest starting with a 10% invitation rate and monitoring it closely for the first few days. Sites with high traffic may find that their needs are met with an invite rate of 2-4%, while lower traffic sides may need to ask 30% of their traffic.
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