The attached Excel file "FridayData_final.xlsx" contains data on the daily volume of trades for stock XYZ (note that there is no trading on Saturdays or Sundays, and we'll assume there are no holidays). The Vol column contains the volume of trades on each day, the Mon, Tue, Wed and Thu columns are dummy variables indicating the day of the observation and the Day_num column is the days from the start of the data, where day 105 is today. If we run a aggression on Vol using Day_num and the day-of-week dummy variables, we obtain the following results: