PSI Tennis App 與 Fourty Love 使用情況與統計

The Performance Stat Index (PSI) was first introduced in 2009 in the form of a workbook for players on the ATP Challenger circuit to make them aware of strengths and weaknesses as well as get an overall view of their performance. Two more indexes were later added to the PSI for players in the intermediate and more advanced player range right below the highest level Index used on the ATP Challenger circuit. Index 1: players with UTRs 3-6.99 Index 2: players with UTRs 7-10.99 Index 3: players with UTRs 11+ A statistical algorithm adds up the total RATIO DIFFERENCE of WON (Good Shots) to LOST (Bad Shots) points in a set. The algorithm then calculates to find the AVERAGE of points either won or lost PER GAME in the set. We refer to these average numbers of points as PSI Ratings. Good Shots = Unreturned Serves, Winners, Forced Errors Bad Shots = Double Faults, Unforced Errors, Missed Makeable Shots After a set is played, both players receive PSI Ratings. If the player’s final PSI Ratings are positive, it means they won more points than lost. If the player’s final PSI Ratings are negative, it means they lost more points than won. At the core of the app are the three indexes that ultimately bestow the PSI GRADES. Three areas of a player’s performance are graded within each designated Index; SERVICE PERFORMANCE, GROUNDSTROKE AND AUXILIARY, and OVERALL PERFORMANCE. All areas consist of uniformed parameters of Good Shot/Bad Shot point averages that make up each Index established through years of research of charting competitive matches at all levels of the game. The following are the PSI PERFORMANCE GRADES. Excellent Performance Above Average Performance Solid Performance Below Average Performance Poor Performance Because the total number of shots recorded can fluctuate, ratios can vary from a 1 to 1.1 ratio to a 1 to 1.9 ratio and so on. A point of reference (midpoint) and closest to Index 2 OVERALL PERFORMANCE parameters is this example. Excellent Performance 3 Good Shots to 1 Bad Shot Ratio Above Average Performance 2 Good Shots to 1 Bad Shot Ratio Solid Performance 1 Good Shot to 1 Bad Shot Ratio Below Average Performance 1 Good Shot to 2 Bad Shot Ratio Poor Performance 1 Good Shot to 3 Bad Shot Ratio Index 1 will have a lower threshold to Solid. Index 3 will have a higher threshold to Solid. Terms of Use EULA: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/