There are 1000 sophomores in a middle school, and the math scores in the mid-term exam obey the n (85,25) normal distribution. How many students in this 1000 are below 75 points?
B is chosen because it obeys the normal distribution n (85 85,25), and the symmetry axis of B is x = 85μ = 85δ = 5: p (75 ≤ x ≤ 95) = 0.9544 ∴ p (x ≤ 75) =? (1-0.9544)=0.228 ∴ Number of people 0.228×1000 = 22.8 ∴ Number of people ∴ Materials 23.