A researcher is interested in the number of days that successful athletes train to run a full marathon. She gets the workout logs for one year for all the athletes who completed a specific marathon in less than four hours. On the average, these athletes of the past trained for 305 days per year. She is in charge of the training for 20 athletes. After they run the marathon, she wonders whether their training differed in amount from the training of successful athletes in the past. She records the number of days of training for her 20 athletes. She uses SPSS to conduct a one-sample t test to determine if her athletes trained a different number of days than 305.

The sample statistics from the SPSS analysis are shown below. What is the sample mean?