Confidence Intervals for Correlation and Proportion
First, this section shows how to compute a confidence interval for Pearson's correlation. The solution uses Fisher's z transformation. Then, it explains the procedure to compute confidence intervals for population proportions where the sampling distribution needs a normal approximation.
Question 1 out of 3.
Why do we subtract 0.5/N from the lower limit and add 0.5/N to the upper limit when computing a confidence interval for the population proportion?
The estimate of the population proportion is slightly biased, and we need to correct for it.
Question 2 out of 3.
Question 3 out of 3.
A researcher was interested in knowing how many people in the city supported a new tax. She sampled 100 people from the city and found that 40% of these people supported the tax. What is the upper limit of the 95% confidence interval on the population proportion?