Kumon promotes a method of studying mathematics that it claims develops mathematical ability. Do data support this claim? In one particular question on the TIMS exam, a random sample of 400 non-Kumon students resulted in 73 getting the correct answer. For the same question, a random sample of 400 Kumon students resulted in 130 getting the correct answer. Perform the appropriate test to substantiate Kumon's claims. Are there any confounding factors regarding the claim?