and in what ways can you raise/decrease it?

thanks

TSR is a weighted system that does not take PSR into account by any means. Factors taken into consideration are: Kills, Deaths, Assists, Creep Kills (adjusted for EM), Creep Denies (adjusted for EM), XP/min (adjusted for EM), Gold/min (adjusted for EM), Wards placed, and Win percentage. Each factor is weighted based on the average player. Statistics from the average player are gathered using game data from millions of matches. The statistics of a given player are compared to that of a player slightly better than average. Creep denies, creep kills, XP/min, and gold/min are negatively adjusted based on the player's EM percentage. The formula also adjusts itself based on the average game-length of the player. TSR is usually updated bi-monthly; when statistically significant game data is accumulated.

essentially its useless if you only play mmr because you cant stack your team

if you could only use 2 stats to rate someone, MMR and TSR are probably the best 2 metrics to use to rate someone

my mmr is 1700, but i'm acutally a 1450 player