It's often useful to know the quartiles of a dataset. The quartiles define the lowest quarter, lowest half, and lowest three quarters data points. Those are typically called q1, q2, and q3. I also like to include q0 and q4, which are the min and max.
q2 is just the median of the dataset. q1 is the median of the lower half of the dataset. And q3 is the median of the upper half of the dataset.
Write a function which calculates the quartiles of a sequence of numbers. You will need to be able to calculate the median (which you can look up easily).