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A field test for a new exam was given to randomly selected seniors. The exams were graded, and the sample mean and sample standard deviation were calculated. Based on the results, the exam creator claims that on the same exam, nine times out of ten, seniors will have an average score within 6% of 80%.

Is the confidence interval at 90%, 95%, or 99%? What is the margin of error? Calculate the confidence interval and explain what it means in terms of the situation.

Respuesta :

shinmin
The confidence interval would be 90% Probability that mean lies between 74% and 86% is 90% Prob( 74 <= X-bar<= 86) = 0.9 So the confidence interval is [74, 86] with 90% confidence that the actual population mean lies inside the interval. The error margin would be 6%. In 9 out of 10 the confidence interval for similar samples of seniors will have the true mean of the population of senior scores. 

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