What do you think of my goalkeeper rating system?

Question

I asked this question before, but everyone liked it except for one who wanted an example, so i'll give an example in this new question. Here are the old details:

I don't think that it's all that accurate, so I want to see what others think. If you have any suggestions, I gladly welcome them. Whoever has the best suggestions (in my opinion) will get best answer. Here's the system:
PCT = Save Percentage
PPCT = Penalty Kick Save Percentage
SV = Saves Made
PG = Penalty Kick Goals Given Up

Rating = (PPCT * 0.1)+(PCT * 0.9)-(PG * 0.75)+(SV * 0.05)

Joe Brown faces 100 shots, and saves 75 of them. He also faces 4 PKs, one of which he saves.

Rating = (25 * 0.1)+(75 * 0.9)-(3 * 0.75)+(75 * 0.05)
Rating = 2.5+67.5-2.25+3.75
Rating = 71.5 (fairly average)

Answer 1

i think this isn't an accurate system as what if they are having a bad day or season and vice versa? that doesn't tell the overall rating that tells you what form they are in, well that's what i think

Answer 2

Basically you have a good idea, but I think it needs more effort to improve the formula.

Firstly, your variables seems confusing. Are all variables need to be in percentage or in the amount? I think percentage is better, but you must make sure that all variables are in the same unit of measure.

Secondly, how can you put such great emphasis on Save Percentage (PCT) comparing to Penalty Kick Save Percentage (PPCT)? Yes, of course goalkeepers usually do more save in a play comparing to penalty saves. But don't you think saving penalty should earn more emphasis since it is very difficult, and it's the time when a goalie is tested in term of determination, intelligence and dilligence (Do you know how Jens Lehmann managed to save some penalties in World Cup 2006 in Germany vs Argentina match? He learned history and movements of opponents' penalty takers before! Some other goalies seems to have very good reflex and anticipation so that they can save the penalty). Saving a penalty may lift up morale of the whole team. In the other hand, in can frustrate opponents because they might see that there is an 'invisible wall' in front of your goal.

Thirdly, what about a goalie that managed to do saves but his experience is still very minimum? Maybe he was just lucky for 1 or 2 games. You can learn statistics theories to improve your formula.

Cheers!

Answer 3

I have no idea what are you talking about. But you don't mention something that to me is very important: the whole defense. Many goalkeepers play well because they have a good defense in front of them. Like Italian goalkeepers. I appreciate more goalkeepers who play well with a weak defense.

Answer 4

i know nothing about math, but i think u r correct, great effort

Answer 5

i suck at math but it looks good