For example, to study whether baldness is related to heart disease, remember that baldness is 1 and baldness is-1.

If the disease is 2 and the disease is -2, then a =1-2b =12c =-12d =-1-2.

The formula k2 = n (ad-BC) 2/(a+b) (c+d) (a+c) (b+d).

The key S ′ = 0 is to find the maximum X value of S, and then find the maximum S. ..

Pay attention to x>0, y-0.

The unit is Celsius, and the calculation formula is: k = (T850-T500)+TD 850-(T700-TD 700).

Extended data:

(1) put forward the original hypothesis:

H0: The distribution function of population x is F(x).

If the population distribution is discrete, it is assumed to be specific.

H0: the distribution law of population x is P{X=xi}=pi, i = 1, 2. ...

(2) If necessary, divide the value range of group X into k disjoint units A 1, A2, A3, …, Ak.

A 1=(a0，A 1)，A2=(a 1，A2)，...，Ak=(ak- 1，Ak)，

A0 can be-∞, ak can be+∞, and the division of intervals depends on the specific situation, but the number of sample values contained in each cell should not be less than 5, and the number of intervals K should not be too large or too small.

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