Title: Confidence Intervals and Levels | Educational Research Basics by Del Siegle
Headings: Confidence Intervals and Levels
Confidence Intervals and Levels
Content: Confidence Intervals and Levels | Educational Research Basics by Del Siegle
Confidence Intervals and Levels
The confidence interval is the plus-or-minus figure usually reported in newspaper or television opinion poll results. For example, if you use a confidence interval of 4 and 47% percent of your sample picks an answer you can be “sure” that if you had asked the question of the entire relevant population between 43% (47-4) and 51% (47+4) would have picked that answer. The confidence level tells you how sure you can be. It is expressed as a percentage and represents how often the true percentage of the population who would pick an answer that lies within the confidence interval. The 95% confidence level means you can be 95% certain; the 99% confidence level means you can be 99% certain. Most researchers work for a 95% confidence level. When you put the confidence level and the confidence interval together, you can say that you are 95% sure that the true percentage of the population is between 43% and 51%. Factors that Affect Confidence Intervals
The confidence interval is based on the margin of error. There are three factors that determine the size of the confidence interval for a given confidence level.