High school math, for example. (2) How to calculate stratified sampling?
Hello, I'm glad to answer your question. Analysis: (1) ∵ 1000 members, the number of people who walk quickly within 3 or 5) is ∴ 0.02× 2×100 = 0.04×100 = 4×10 = The number of people walking in 9) is ∴ 0.05× 2×1000 = 0.1×100 =1×100 =100. And ∵ the number of striding steps is ∴ 0.05× 2×1000 = 0.1×1000 =1× 65438. ∴40+60+ 100+ 100= 100+ 100+ 100=200+ 100= 100×3=300 ; ∴ Among 1000 members, 300 people walk less than 1 1000 steps. (2) ∵ According to the stratified sampling method, three people were selected from 1 1 3, ∴ marked as a 1, a2, a3, ∴, and each person scored 90 points. And ∵ in 13, 15), to draw two people, ∴ marked as b 1, b2, ∴ everyone's score is110; ∵ in 15, 17), 1 person should be extracted, ∴ marked as c 1, ∴ everyone's score is130; And ∵ 2 out of 6 people, ∴ a 1b 1, a 1b2, a 1c, a2b 1, a2b2, a2c, a3b 1. ∴ * * 12 method, ∵ assuming that two people are selected from six people, and the sum of their integrals is not less than 200, it is divided into event a, ∴ then: ∴ p (a) =12/15 = (. ∴ 2 people are randomly selected from 6 people, and the probability that the sum of their integrals is not less than 200 points is 4/5. (3) The median is 37/3.