STATISTICAL TECHNIQUES AND TOOLS
CONFIDENCE INTERVALS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.Find the Margin of Error to two decimal places.
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1.90
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1.89
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1.899
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1.99
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Explanation:
Detailed explanation-1: -e.g. IQ is normally distributed (mean = 100, SD = 15). 68% of people have IQs between 85 and 115 (100 +/-15). 95% have IQs between 70 and 130 (100 +/-(2*15). 99.7% have IQs between 55 and 145 (100 +/-(3*15).
Detailed explanation-2: -b) Approximately 95% of the IQ scores are expected to be within the interval 68 to 132 IQ points.
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