(精品)Chapter7Intervalestimation.ppt

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1、Chapter 7 Interval estimationSection 3 Determine the necessary sample size1.Necessary sample size（必要的样本容量，P269）1)Factors affecting the necessary sample size2)Necessary sample size:Within the limit of the estimation accuracy（budget）,the size needed.Relationships between sample size and accuracyChapte

2、r 7 Interval estimation2.Determine the sample size based on acceptable error（允许误差，accuracy）(1)Determine n when estimating(P270)With replacementNote:Factors affecting the sample sizeChapter 7 Interval estimation Without replacementChapter 7 Interval estimation(2)Determine n when estimating P With rep

3、lacement(P273)Without replacementChapter 7 Interval estimationExample A cold storage try to investigation the deteriorate rate of a shipment of eggs.According to previous investigations,the deteriorate rates are 27%、25%、24%.If the acceptable erroracceptable error is not larger than 5%,the confidence

4、 of the estimation is 95%.Then how many eggs are needed for the sample?Solution：Z=1.96，Ep=5%，P1=27%，P2=25%，P3=24%Chapter 7 Interval estimationEx A cold storage try to investigation the deteriorate rate of a shipment of eggs.If the acceptable error is not larger than 5%,the confidence of the estimati

5、on is 95%.Then how many eggs are needed for the sample?(P=0.5,so n=385 eggs).Ex A pharmaceutical factory need to check the number of tablets in bottles.So they pick 100 bottles randomly,the mean number of tablets is 101.5 and the S.D is 3.Estimate the 99.73%confident interval of the mean number of t

6、ablets in bottles.If the acceptable error halved,then how many bottles need to be sampled?Chapter 7 Interval estimationCase study Is the absence rate higher than 20%(20 pts)?The absence of students has became a serious problem in universities now.In a recent random inspection,the inspecting team fou

7、nd that the absence rate is higher than 20%.To check this number,the inspecting team hired a investigation agency to do a study on the absence of students.500 students are randomly picked.Among them,only 375 students have never been absent.Questions:(1)Based on the sample,whats the absence rate in t

8、his university?(2)Is the absence rate higher than 20%in this university?(=0.05);(3)If error has to be no larger than 5%,then how many students have to be sampled?(4)Describe the essence of statistical estimation.Chapter 7 Interval estimationCase study Is the absence rate higher than 20%(20 pts)?In a

9、 recent random inspection,the inspecting team found that the absence rate is higher than 20%.To check this number,the inspecting team hired a investigation agency to do a study on the absence of students.500 students are randomly picked.Among them,only 375 students have never been absent.Questions:(

10、2)Is the absence rate higher than 20%in this university?(=0.05);(3)If error has to be no larger than 5%,then how many students have to be sampled?(4)Describe the essence of statistical estimation.Chapter 7 Interval estimationCase study Is the absence rate higher than 20%(20 pts)?In a recent random i

11、nspection,the inspecting team found that the absence rate is higher than 20%.To check this number,the inspecting team hired a investigation agency to do a study on the absence of students.500 students are randomly picked.Among them,only 375 students have never been absent.Questions:(3)If error has to be no larger than 5%,then how many students have to be sampled?(4)Describe the essence of statistical estimation.