statistical analysis in excel definitions confidence level

There are three factors that determine the size of the confidence interval for a given confidence level: The wider the confidence interval you are willing to accept, the more certain you can be that the whole population answers would be within that range.įor example, if you asked a sample of 1000 people in a city which brand of cola they preferred, and 60% said Brand A, you can be very certain that between 40 and 80% of all the people in the city actually do prefer that brand, but you cannot be so sure that between 59 and 61% of the people in the city prefer the brand. 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%. Most researchers use the 95% confidence level. The 95% confidence level means you can be 95% certain the 99% confidence level means you can be 99% certain. It is expressed as a percentage and represents how often the true percentage of the population who would pick an answer lies within the confidence interval. The confidence level tells you how sure you can be.

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 interval (also called margin of error) is the plus-or-minus figure usually reported in newspaper or television opinion poll results. Sample Size Calculator Terms: Confidence Interval & Confidence Level

Statistical analysis in excel definitions confidence level