In the pre-primary comprehensive ability test for 6-year-old children, the average score was 58 for the children who attended A preschool all day for 9 months, and the average score was 52 for the 9 months who attended the A preschool only in the morning, and only in the afternoon  The average score of 9 months in preschool A is 51; the average score of 9 months in preschool B is 54; and those 6-year-olds from low-income families who have not attended preschool, before entering the same primary school The average score in the comprehensive ability test is 32
Statistically, the difference between 32 points and the other scores mentioned above is significant
More testing is required to make a plausible hypothesis.