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AA ? 20. Confidence Intervals: Values of o A random sample of size 36 is drawn from an r distribution. The sample mean is 100. (a) Suppose the x distribution has o = 30. Compute a 90% confidence interval for u. What is the value of the margin of error? (b) Suppose the r distribution has o = 20. Compute a 90% confidence interval for . What is the value of the margin of error? (c) Suppose the x distribution has o = 10. Compute a 90% confidence interval for u. What is the value of the margin of error? (d) Compare the margins of error for parts (a) through (c). As the standard deviation decreases, does the margin of error decrease? (e) Critical Thinking Compare the lengths of the confidence intervals for parts (a) through (c). As the standard deviation decreases, does the length of a 90% confidence interval decrease