Chapter 20 estimating proportions with confidence

Answer: plus or minus .044 (or 4.4%)

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Answer: plus or minus .044 (or 4.4%).

{Oranges narrative} Suppose the grocery store who ordered the oranges will reject the shipment if they believe, based on these sample results, that more than 10% of the bags in the entire truckload are underweight. Based on our sample, will they have to return this shipment? Explain your answer.

Answer: no; a 95% confidence interval for the proportion of bags in the shipment that are underweight is .006 TO .094 (5% plus or minus 4.4%). Since .10 (10%) IS NOT IN THIS INTERVAL, THE SHIPMENT IS NOT REJECTED.

Using one divided by the square root of the sample size is known as a ‘conservative’ formula for the margin of error for a sample proportion. Explain what that means.

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