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Unformatted text preview: Review and Examples If you want to construct a conﬁdence interval for the population mean, you can determine the sample size you should use for your study before collecting your data. If you want your conﬁdence interval to have a margin of error of size E , then you should have a sample of at least (zα/2 )2 σ 2 n= E2 A conﬁdence interval for a population proportion is p ± zα/2 ¯ p(1 − p) ¯ ¯ . n The desired sample size to achieve a margin of error E is (zα/2 )2 p∗ (1 − p∗ ) n= E2 Example: A survey of 369 working parents found 200 who said they spend too little time with their children because of work commitments. a. What is the point estimate of the proportion of the population of working parents who feel they spend too little time with their children because of work commitments? b. What is the margin of error for a 95% conﬁdence interval?
1 c. What is the 95% conﬁdence interval for the proportion of working parents who feel they spend too little time with their children because of work commitments? d. What sample size should have been used if a margin of error of 0.03 was desired? 2 ...
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This note was uploaded on 01/24/2011 for the course STATISTICS 19897 taught by Professor Jager,abigaill during the Fall '10 term at Kansas State University.
 Fall '10
 Jager,AbigailL

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