I use an estimation jar in my classroom. Each week I put different types of candy in the jar. The students have all week to use different estimation strategies to try and figure out the best estimation. At the end of the week we have a mini math lesson looking at our estimation data set. We place everyone's guesses on our chalkboard and then determine minimum, maximum, and range for the data set. In the end based on numerical clues I give the class, they determine whose "guess" is the closest to the actual number of items in the jar. That student wins the candy for the week and this certificate. It is a fun way to practice our statistical landmarks and our estimation.