Use the given degree of confidence and sample data to construct a confidence interval for the population proportion p. Round to three decimal places. n = 74, x = 12; 95% confidence. Navigation: PRINCIPLES OF STATISTICS > Confidence intervals. Interpreting a confidence interval of a mean. Scroll. While confidence intervals are usually expressed with 95% confidence, this is just a tradition. Confidence intervals can be computed for any desired degree of confidence.
proportion (sample proportion). A confidence interval (CI) is a range of values, computed from the sample, which is with probability of 95% to cover the population proportion, π (well, you may use any pre-specified probabilities, but 95% is the most common one).
When calculating a confidence interval involving proportions, you should keep the following in mind: The confidence levels can be very inaccurate unless your sample size sample is very large. The actual confidence level is often less than the confidence level you specify.