What is a Confidence Interval? Statisticians use a confidence interval to describe the amount of uncertainty associated with a sample estimate of a population parameter. How to Interpret Confidence Intervals Suppose that a 90% confidence interval states that the population mean is greater than 100 and less than 200.

A 95% confidence interval is a range of values that you can be 95% certain contains the true mean of the population. We can visualize this using a normal distribution (see the below graph). For example, the probability of the population mean value being between -1.96 and +1.96 standard deviations (z-scores) from the sample mean is 95%. What is a Confidence Interval? Statisticians use a confidence interval to describe the amount of uncertainty associated with a sample estimate of a population parameter. How to Interpret Confidence Intervals Suppose that a 90% confidence interval states that the population mean is greater than 100 and less than 200.

Confidence intervals are your frenemies. They are one of the most useful statistical techniques you can apply to customer data. At the same time they can be perplexing and cumbersome. But confidence intervals provide an essential understanding of how much faith we can have in our sample estimates ... A confidence interval is an interval estimate combined with a probability statement. This means that if we used the same sampling method to select different samples and computed an interval estimate for each sample, we would expect the true population parameter to fall within the interval estimates 95% of the time. As an example, consider a researcher wishing to estimate the proportion of X-ray machines that malfunction and produce excess radiation. A random sample of 40 machines is taken and 12 of the machines malfunction. The problem is to compute the 95% confidence interval on π, the proportion that malfunction in the population. A confidence interval is an interval estimate combined with a probability statement. This means that if we used the same sampling method to select different samples and computed an interval estimate for each sample, we would expect the true population parameter to fall within the interval estimates 95% of the time. A 95% confidence interval is a range of values that you can be 95% certain contains the true mean of the population. We can visualize this using a normal distribution (see the below graph). For example, the probability of the population mean value being between -1.96 and +1.96 standard deviations (z-scores) from the sample mean is 95%.

This means that if we repeatedly compute the mean (M) from a sample, and create an interval ranging from M - 23.52 to M + 23.52, this interval will contain the population mean 95% of the time. In general, you compute the 95% confidence interval for the mean with the following formula: Confidence Intervals for the Difference Between Two Means . Introduction . This procedure calculates the sample size necessary to achieve a specified distance from the difference in sample means to the confidence limit(s) at a stated confidence level for a confidence interval about the difference in