A researcher would like to examine how the chemical tryptophan, contained in foods such as turkey, can affect mental alertness. A sample n=19 college students is obtained and each student's performance on a familiar video game is measured before and after eating a traditional Thanksgiving dinner including roast turkey. The average score decreased by 20 points after the meal with SS=1727 for the difference scores. Calculate the report the value of the appropriate test-statistic to two decimal places.