let a, b and c be three events, the proposition a-(b-c)=(a-b)-c is true.
let a, b and c be three events, if ab=ϕ and c⊂a, then bc=ϕ .
let a, b and c be three events, the proposition(a∪b)-b=a is true.
let a, b and c be three events, the proposition is true.
let a and b be incompatible, and p(a)=0.2, p(b)=0.5. calculate p(a∪b)= .(rounded to four decimals)
let a, b and c be three events, the proposition p(a∪b|c)=p(a|c) p(b|c) is true.
there are two boxes of the same kind of goods: the first box contains 50 pieces, including 10 high-quality products; the second box contains 30 pieces, including 18 high-quality products. now randomly open a box and take one from the box at random. the probability of getting a high-quality product is _________.(rounded to four decimals)
the prior probability and the posterior probability must be different.
let a and b be independent events. which of the following options is true ( ).
supposed p(a)=0.4 , p(a∪b)=0.9, then 。 so which condition should be required by a and b.
let a, b be two events, which of the following options is true ( ).
the distribution function of x is f(x). so which of the following options is true ( ).
which random trials do not belong to the poisson distribution. ( )
which of the following properties don't belong to the poisson flow? ( )
let , and . it can be get that ( ).
let be three random variables, and ，， . we define . it can be get that ( ).
let , and . the distribution of is ( ).
let the joint probability density function of be the constant equals to（ ）.
which of the following description about is wrong ( ).
which one of the upper and lower limits of double integration is correct in the following integration? ( ).
in the video, the type integral of the joint density on the area can be expressed as ( ).
when we got the density function of by the convolution formula, how can we obtain the density function of . ( )
let x and y be independent with . then is a discrete random variable. ( )
review the video please, the value range of is ( ).
review the video please, the value range of is ( ).
if , then ex and dx are respectively ( ).
let let x1, x2,...,xn be random variables, then . ( )
the mathematical expectations of x1, x2,...,xn have linear property if and only if x1, x2,...,xn are independent.
in the video, are independent. ( )
in the video, and are independent. ( )
if , then x and y must be in independent.
if x~p(2)(poisson distribution), then ( ).
let x1, x2,... be independent and identically distributed random variables, and ,then ( )
according to the table of question (2), the empirical distribution function is
let be a random sample from population, and be a sample mean. the ( ).
let be a random sample from population, and is unknown. ，. then follows ( ).
let be a sample from a n(0,1) population. it can be seen that ( ).
let be a sample from a population, and are unknown. , . then follows ( ).
let be a sample from a population, and are unknown. , . which of the following is the correct statement ( )
which of the following statements is correct about parameters and parameter spaces. ( )
let be a population. then the moment estimator of a and b must be .
moment estimation is always reasonable
in the likelihood function , which following description of the sample is correct ( ).
whether the solution of the likelihood equation must be judged whether the second derivative is less than 0
the likelihood estimator can always be obtained from the likelihood equation .
which group is the sample of the population . ( )
is an estimator or an estimate in the video example? ( ).
the aller the , the higher the significance level.
in order to test whether the restaurant menu is valid, what can we yze. ( )
which test does belong to when the variance is known
for tests where the variance is known, which one is correct about the type ii error?
for tests where the variance is known, the t test should be used.
for the normal population, the test of the hypothesis belongs to ( ).
for the normal population, which distribution should be for the test of the variance when the mean is known.
the null and alternative hypotheses of the chi-square fit test are ( ).
when judging the test h0: f(x)=f0(x); h1: f(x)≠f0(x) about population distribution, which of the following conclusions is wrong?
what is the meaning of the regression coefficient in the linear regression model?
which of the following assumptions about the regression model is wrong.
which of the following correlation coefficients is wrong?
what is the sum .
if the correlation coefficient is equal to 0, what is the relationship between the two variables （ ）.
let a, b and c be events such that p(a)=p(b)=p(c)=1/3, p(c|a∩b)=1/2, and a and b are independent. calculate p(a∩b|c)=( ).