The authors of the paper "Striatal Volume Predicts Level of Video Game Skill Acquisition" studied a number of factors that affect performance in a complex video game. One factor was practice strategy. Forty college students who all reported playing video games less than 3 hours per week over the past 2 years and who had never played the game Space Fortress were assigned at random to 1 of 2 groups. Each person completed 20 2-hour practice sessions. Those in the fixed priority group were told to work on improving their total score at each practice session. Those in the variable priority group were told to focus on a different aspect of the game, such as improving speed score, in each practice session. The investigators were interested in whether practice strategy makes a difference. They measured the improvement in total score from the first practice session to the last. Improvement scores (approximated from a graph in the paper) for the 20 people in each practice strategy group are given here. Fixed Priority Practice Group 1,100 1,900 1,950 2,400 2,550 3,750 3,850 3,900 4,050 Variable Priority Practice Group 2,650 2,500 3,550 3,450 3,550 4,050 4,100 4,100 4,550 5,000 6,050 1,150 1,250 2,250 3,150 3,350 3,750 5,500 4,050 4,050 4,350 4,850 5,700 5,650 5,850 6,000 6,350 6,850 6,750 6,950 7,700 (a) What is the appropriate symbol for the point estimate of the population mean? S (b) Determine the point estimate for the population mean improvement in total score for all gamers who follow the "Fixed Priority Practice" strategy.