The result of the previous chapter is quite interesting! It turns out that the top 10 combinations of store and week with the highest sales are during the last but one week of December! What could be the reason for this? Perhaps the upcoming Christmas - people start preparing for the holiday, buying gifts, and so on.

There is a column called 'Holiday_Flag' with only 2 possible values: 1 if the week contains a major holiday, and 0 if it does not. Let's compare the median sales for weeks with and without holidays.