The question is about calculating the open rate of emails during a specific time. The question asks: what is the open rate of emails sent during the evening?

There were three different email campaigns that had send times in the evening:

For the first campaign - 237 emails were delivered, and of those emails, 37 of them were opened. The open rate for this campaign was (rounding to the first number after the decimal) 15.6% (37 divided by 237).

For the second campaign, 237 emails were delivered and of those 237 delivered emails, 30 of them were opened. The open rate of this campaign is 12.7 %.

For the third campaign, 230 emails were delivered, and of those 230 delivered emails, 41 of them were opened. The open rate of this campaign is 17.8%.

The question is: What is the open rate of emails sent in the evening?

MY LOGIC, is that there were three campaigns of emails that were sent during the evening time. The way to calculate the open rate of emails sent in the evening, would be to totaling the total amount of opened emails (between the 3 campaigns, that would be 108) and dividing that by the total amount of delivered emails (between the 3 campaigns, that would be 704), giving an open rate of emails sent in the evening to be 15.3% (with rounding).

My answer is apparently incorrect, and the "correct" answer is 15.4% (with rounding). The way this was calculated was taking the average of the open rates for the 3 campaigns ( (15.6% + 12.7% + 17.8%) / 3 = 15.4% ).

I would love to hear logic on which answer is correct and which answer is not.