(一) 卡方分布 研究者常有兴趣在某一属性或变项的观察次数上，由抽样实验所得到的次数 称为观察次数(observed frequency)(O)，常会分成几个类别或称为水准(level)，例如 在「性别变项的次数观察上，可分为「男、「女两个类别分别计数；喜恶程 度...
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2005年克山病、大骨节病、碘缺乏病防治情况 ... 年各地区农村乡镇卫生院及床位、人员数 Number of Township Health Centers and Their Beds and Personnel by Region in 2005 年各地区村卫生室及人员数 Number of Village Clinics and Their Personnel by Region in 2005 年人口状况 Population Status in 2002 ...
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观察的联合次数 Observed joint frequency
就是用这样的办法，通过观察这缓慢的振动和计算一天中的振动次数，卡文迪什计算出了地球的确切的重量。
This could not be otherwise; and from the slowness of a vibration, or from the small number of vibrations in a day, Cavendish computed the real weight of the earth.
交易发生的次数也可以提供关于价值的附加信息，它能告诉观察家们购买商品的价值随时间有何变化。
Additional information about value is obtained by the rate at which transactions occur, telling observers the extent to which the purchase of the good has value over time.
最关键的是，研究者们发现当参与者们把精力集中于观察慢跑者手与头接触的次数时，其注意到那场打斗的概率则会大大降低。
Crucially, the researchers found that participants were far less likely to notice the fight when they were focusing their attention on how many times the jogger touched his hat.
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