统计学CH10 英文版
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Chapter 2 Statistic ReviewA.Random variables;1.expected value:Define :X is a discrete random variable, “ the mean (or expected value)of X " is the weighted average of the possible outcomes, where the probabilities of the outcomeserve as the appropriate weight.p i is ith of prob.,i=1,2, ……nInterpretation:The random variable is a variable that have a probability associated with each outcome. Outcome is not controlled。
Discrete random Var。
: has finite outcome,or outcome is countable infinite.Continuous random Var。
:uncountable infinite outcome,the probability of each outcome is small because of too many numbers.For normal random Var。
, probability density function is used to calculate the probability between the are.E( ):the expectations operator,→… “ sample mean”, used to estimateThe is changed from sample to sample. is not a fixed on time,the outcome selected should not be the same. There is prob。