Practice Confidence Interval in Statistics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

A range of values, calculated from sample data, that is likely to contain the true population parameter with a specified level of confidence.

Instead of saying 'the average is 50,' you say 'I'm 95% confident the average is between 47 and 53.' The interval acknowledges uncertainty from sampling.

Example 1

hard
A sample of 100 students has a mean test score of \bar{x} = 72 with population standard deviation \sigma = 10. Construct a 95% confidence interval for the population mean.

Example 2

hard
A 95% confidence interval for the mean weight of apples is (150g, 170g). Interpret this interval.

Example 3

hard
A sample of 64 has \bar{x} = 50 and \sigma = 8. Find the 99% confidence interval (z^* = 2.576).

Example 4

hard
A 90% confidence interval for a population mean is given as 68 to 74. What are the sample mean and the margin of error?
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