统计题（Statistical questions）
0. what is the standardization law? What is the significance of standardization? What criteria are ud to meet the material requirements and the direct method?
The standard method is two or more than two of total numbers were compared in order to eliminate the internal structure of the different effects of the uniform standards, different groups of internal mean method after adjustment were compared.
When the number of obrvation cas in each group is large enough and the number of positive cas is known, the direct method can be ud
1 the significance of medical reference value range and the method of determining it
The meaning is the fluctuation range of data determined by a certain probability, as the reference index to judge the normal and abnormal in clinic
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Methods: normal distribution method, steps: 1> normality test, 2> if normal, calculated mean X and standard deviation S, 3> estimation range of reference value x (-) + ua/2S
2 how do four table data undergo hypothesis testing?
1. establish hypothesis testing and establish inspection level
H0: the sample rate of the two classified variables is the same
H1: the data rate of the two classified variables is different
A=0.05
2. compute test statistics
A., if n>=40, but with 1<T<5, requires continuity correction of X2 values
B. If n<40 or T<=1, the exact probability method
3. determine the P value and draw inferences
3, talk about your understanding of hypothesis testing P values
The meaning of the P value is the probability that the total random sampling from H0 is equal to and equal to or equal to or equal to the probability of the test value obtained not less than the existing sample. If: p<=a, then the conclusion rejected H0 accept H1, according to a test level, get "difference
is statistically significant" conclusion. On the other hand, p>a, to H0, according to the a test standard, "no significant difference" conclusion, but not "no difference" conclusion, only "according to the test results, still can't believe that there is difference between" conclusion, becau H0 is not equal to refu to accept H0.
4, briefly describe the differences and connections between type I errors and type II errors, and understand the practical significance of the two types of errors.
The type I error refers to the establishment of the H0 I actually refud to make mistakes, "abandoning the truth" the probability of a, the type II error refers to the error from the "pudo" received the H0 was not made, the probability of B. When the sample is n, the smaller the A, the bigger the B; on the contrary, the larger the A, the smaller the B; if the application should focus on reducing a, then take the a=0.05; if the focus is reduced by B, take a=0.10 or 0.20, or even higher.
心的束缚5. briefly describe the relation between normal distribution, two term distribution and Poisson distribution.
Normal distribution: the estimation of the frequency distribution of the normal distribution of continuous random variables
发信息>小学生敬礼图片Two distribution: there were only two possible outcomes in each trial, and they were antagonistic; each experiment was independent and independent of the other test results
Poisson distribution: a discrete distribution of a single parameter, reprenting the average number of times in a unit, time, or space
When the n is larger or the PI is not clo to 0 or 1, the two term distribution can be regarded as approximately normal distribution和附
Poisson can be considered as a limit of the two distribution, that is, when Pi is small and n tends to infinity, the two term
distribution is approximately Poisson distribution, and when >=20, we can approximate it by normal distribution
6. what are the indicators that describe the trend of concentration? What are the similarities and differences in its scope of application?
Mean: normal or approximately normal distribution
Geometric mean: geometric ries or lognormal distribution
Median: the data is skewed distribution; irregular distribution; uncertain data (opening data) at one or both ends.
7 what is hypothesis testing and can be illustrated by examples
Hypothesis testing is the u of small probability apagoge thought, make the first two opposite to the general characteristics of statistical assumptions, and then calculate the test statistic in H0 was established under the condition that the probability of getting the value of P, a compared to determine the statistical inference process of H0 is established and the probability of a predetermined value
1. establish hypothesis testing and establish inspection level
平心静气的意思H0: the sample rate of the two classified variables is the same
H1: the data rate of the two classified variables is differentafoot
A=0.05
2. compute test statistics
3. determine the P value and draw inferences
8 talk about your assumptions about the conclusions of the tests
The conclusion is bad on the principle of hypothesis testing a small probability event may not occur for the actual test, therefore rejected when testing hypothes may make the type I error, when the tested hypothesis is likely to make the type II error.
9. compare the similarities and differences between standard and standard errors一般现在时练习
The standard deviation of individual differences in size of n = S, and the average combination can make a reference range
Standard error of sampling error size n = - 0 and mean confidence interval can be calculated with the overall mean number
10, how can sampling errors be controlled or reduced in sampling studies?
A reasonable sampling design increas the sample size
11., what is sampling error? Why is sampling error inevitable in sampling studies?
