Title: Understanding Confidence Intervals
Headings: The Use of Confidence Intervals in Inferential Statistics
The Use of Confidence Intervals in Inferential Statistics
The Form of a Confidence Interval
Confidence Level
Margin of Error
Standard Deviation or Standard Error
Different Confidence Intervals

Content: Confidence Level
Attached to every confidence interval is a level of confidence. This is a probability or percent that indicates how much certainty we should be attributed to our confidence interval. If all other aspects of a situation are identical, the higher the confidence level the wider the confidence interval. This level of confidence can lead to some confusion. It is not a statement about the sampling procedure or population. Instead, it is giving an indication of the success of the process of construction of a confidence interval. For example, confidence intervals with confidence of 80 percent will, in the long run, miss the true population parameter one out of every five times. Any number from zero to one could, in theory, be used for a confidence level. In practice 90 percent, 95 percent and 99 percent are all common confidence levels. Margin of Error
The margin of error of a confidence level is determined by a couple of factors.