text: what's the mean, median, mode for the two sets of data? size of litter  1  2  3  4  5  6  7 8 9 #litter         8 10 15 17 25 32 12 8 3 i presume you mean arithmetic mean (there are other forms of mean, such as geometric mean, harmonic mean, etc).   for the mean, just add up the numbers in each data set and divide by the number of data.  for the median, write the numbers in each data set out biggest to smallest and pick the middle number. if there are an even number of data, take the average of the two middle data.  for the mode, pick the data value that appears most often in each set. it is not necessarily unique, however.