18.
“微信运动”是手机
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmi%3EA%3C%2Fmi%3E%3Cmi%3EP%3C%2Fmi%3E%3Cmi%3EP%3C%2Fmi%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
推出的多款健康运动软件中的一款,大学生M的微信好友中有400位好友参与了“微信运动”.他随机抽取了40位参与“微信运动”的微信好友(女20人,男20人)在某天的走路步数,经统计,其中女性好友走路的步数情况可分为五个类别:
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3EA%3C%2Fmi%3E%3C%2Fmath%3E)
、
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E0%3C%2Fmn%3E%3Cmo%3E%E2%88%BC%3C%2Fmo%3E%3Cmn%3E2000%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
步,(说明:“
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E0%3C%2Fmn%3E%3Cmo%3E%E2%88%BC%3C%2Fmo%3E%3Cmn%3E2000%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
”表示大于或等于0,小于2000,以下同理),
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3EB%3C%2Fmi%3E%3C%2Fmath%3E)
、
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E2000%3C%2Fmn%3E%3Cmo%3E%E2%88%BC%3C%2Fmo%3E%3Cmn%3E5000%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
步,
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3EC%3C%2Fmi%3E%3C%2Fmath%3E)
、
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E5000%3C%2Fmn%3E%3Cmo%3E%E2%88%BC%3C%2Fmo%3E%3Cmn%3E8000%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
步,
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3ED%3C%2Fmi%3E%3C%2Fmath%3E)
、
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E8000%3C%2Fmn%3E%3Cmo%3E%E2%88%BC%3C%2Fmo%3E%3Cmn%3E10000%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
步,
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3EE%3C%2Fmi%3E%3C%2Fmath%3E)
、
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E10000%3C%2Fmn%3E%3Cmo%3E%E2%88%BC%3C%2Fmo%3E%3Cmn%3E12000%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
步,且
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3EA%3C%2Fmi%3E%3C%2Fmath%3E)
、
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3EB%3C%2Fmi%3E%3C%2Fmath%3E)
、
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmi%3EC%3C%2Fmi%3E%3C%2Fmath%3E)
三种类别的人数比例为
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmn%3E1%3C%2Fmn%3E%3Cmo%3E%EF%BC%9A%3C%2Fmo%3E%3Cmn%3E4%3C%2Fmn%3E%3Cmo%3E%EF%BC%9A%3C%2Fmo%3E%3Cmn%3E3%3C%2Fmn%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
,将统计结果绘制如图所示的柱形图;男性好友走路的步数数据绘制如图所示的频率分布直方图.
(Ⅰ)若以大学生
抽取的微信好友在该天行走步数的频率分布,作为参与“微信运动”的所有微信好友每天走路步数的概率分布,试估计大学生
的参与“微信运动”的400位微信好友中,每天走路步数在
的人数;
(Ⅱ)若在大学生
该天抽取的步数在
的微信好友中,按男女比例分层抽取6人进行身体状况调查,然后再从这6位微信好友中随机抽取2人进行采访,求其中至少有一位女性微信好友被采访的概率.