Objective C :Sample Size Needed for Estimating the Population Proportion The sample size required to obtain a confidence interval for with a margin of error is given by Round up to the next integer is a prior estimate of If a prior estimate of is unavailable, the sample size required is Round up to the next integer So you can use if proportion is not given Example 1 : An urban economist wishes to estimate the proportion of Americans who own their homes. What size sample should be obtained if he wishes the estimate to be within 0.02 with 90% confidence if: (a) he uses a 2010 estimate of 0.669 obtained from the U.S Census Bureau? He wants: with 90% confidence so use z = 1.65 0.02 = 1.65 SE 0.02 = 1.65 1507.17 round up to 1508. He should sample 1508 Americans so that the estimate is within 0.02 margin of ≈ error at a 90% confidence level. Note: For MML you have to be more precise and use z = 1.645 for 90%CI and z = 1.96 got 95%CI (b) he does not use any prior estimates? If not estimate is given for the proportion, then we use = .50 0.02 = 1.65 1707.5 round up to 1708. He should sample 1708 Americans. Note: if you do not round your answer will be ≈ 1702. Example 2: In a Gallup poll conducted in October 2010, 64% of the people polled answered "more strict" to the following question: "Do you feel that the laws covering the sale of firearms should be made more strict as they are now?" Suppose the margin of
Objective C :Sample Size Needed for Estimating the Population Proportion The sample size required to obtain a confidence interval for with a margin of error is given by Round up to the next integer is a prior estimate of If a prior estimate of is unavailable, the sample size required is Round up to the next integer So you can use if proportion is not given Example 1 : An urban economist wishes to estimate the proportion of Americans who own their homes. What size sample should be obtained if he wishes the estimate to be within 0.02 with 90% confidence if: (a) he uses a 2010 estimate of 0.669 obtained from the U.S Census Bureau? He wants: with 90% confidence so use z = 1.65 0.02 = 1.65 SE 0.02 = 1.65 ≈ 1507.17 round up to 1508. He should sample 1508 Americans so that the estimate is within 0.02 margin of error at a 90% confidence level. Note: For MML you have to be more precise and use z = 1.645 for 90%CI and z = 1.96 got 95%CI (b) he does not use any prior estimates? If not estimate is given for the proportion, then we use = .50 0.02 = 1.65 ≈ 1707.5 round up to 1708. He should sample 1708 Americans. Note: if you do not round your answer will be 1702. Example 2: In a Gallup poll conducted in October 2010, 64% of the people polled answered "more strict" to the following question: "Do you feel that the laws covering the sale of firearms should be made more strict as they are now?" Suppose the margin of
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