You would need to sort the data from smallest to largest
{1,2,4,3,5,3,6,7,8} sorts to {1,2,3,3,4,5,6,7,8}
Note there are 9 values. So 9/2 = 4.5 which rounds down to 4, which means there are 4 values below the median and 4 values above the median. The median is the middle most value
Here is a look at those pair of 4 values each which I have bolded: 1,2,3,3,4,5,6,7,8
Or it might be easier to highlight the median itself rather than whats around it: 1,2,3,3,4,5,6,7,8
