Title: Confidence Intervals in Statistics - Simple Tutorial
Headings: Simple Introduction to Confidence Intervals
Simple Introduction to Confidence Intervals
Confidence Intervals - Example
Confidence Intervals - How Does it Work?
Confidence Intervals - Illustration
Confidence Intervals - Basic Properties
Confidence Intervals or Statistical Significance?
Formulas and Example Calculations

Content: Confidence Intervals - Basic Properties
Right, so a confidence interval is basically a likely range of values for a parameter such as a population correlation, mean or proportion. Therefore, wider confidence intervals indicate less precise estimates for such parameters. Three factors determine the width of a confidence interval. Everything else equal,
lower confidence levels result in smaller intervals: 90% CI's are smaller than 95% CI's and these are smaller than 99% CI's. The tradeoff here is that smaller intervals are less likely to contain the parameter we're after: 90% versus 95% or 99%. More precision, less confidence and reversely. larger sample sizes result in smaller CI's. However, the width of a CI is linearly related to the square root of the sample size.