Yes, you definitely can reset your stats :) Just click the "Reset Stats" button to the right of "Results Summary" on the Dashboard.
Resetting your stats removes your answer data, marks your answered questions unanswered, and resets the score predictor. You will no longer be able to see how many questions you've answered, and you cannot reset only certain questions. However, we at Magoosh can still see how many questions you've done, so resetting your stats does not affect the score guarantee :)
Resetting your stats will not erase your notes and flags. While you won't be able to filter for them in Review ("Only Flagged", "Only with Note") after the reset, you will still be able to filter for them in Practice!