Count only the most recent answer
Currently, answering multiple times means multiple entries per person. It would be more useful to me if students could change their answers, with the most recent answer replacing the previous one(s). I'd use this when results are hidden.
It's true that I can look at their results afterward and filter out the previous answers, but the feature I'm requesting would both (1) make that a simpler process and (2) make the display of results (when shown) more accurate.

Our Change Answer feature is now available! Students may now click “Clear Responses” at the bottom of the page to change their original answer. And, if they are using text message – they may text Clear or Undo to the same number to change their response. Tell us what you think!
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Customer reports giving poll questions in classes. Set it up for 2 or 3 responses allowed because students sometimes send it in too quickly or realize they sent the wrong thing and need to re-send an answer. Other times they enter my keyword “Cimbala” after the poll is already open and they are already logged in from the previous lecture and don’t realize it, so I get lots of responses that are “Cimbala” followed by the real answer. Other times the response from Poll Everywhere is slow and the students panic and text in the same answer again. I end up with lots of multiple answers from the same student. I have to manually sort through all of them in Excel to grade them. What I want is that only the LAST response is reported in the report and into the CSV file that I read into Excel.