The problem with borrowed numbers
Follow-up timing advice circulates as though it were settled. Follow up within a day. Make five attempts. Tuesday morning performs best. Whatever the specific claim, it originated in a particular market with a particular buying process, and it was often calculated on data with the same confounder described below. None of that makes it worthless. It makes it a hypothesis.
The good news is that this is one of the few sales questions a small business can genuinely answer for itself, because the data required is minimal and the analysis is arithmetic rather than statistics. What follows is a method rather than an answer, and the absence of an answer here is deliberate.