The ‘CONFIDENCE’ function is an Excel statistical function that returns the confidence value using the normal distribution. Standard_dev (required argument) – This is the standard deviation for the data range. Alpha (required argument) – This is the significance level used to compute the confidence level. First, type =CONFIDENCE (and then enter an appropriate alpha value. The formula to calculate the prediction interval for a given value x0 is written as: ŷ0 +/- tα/2,df=n-2 * s.e. We use the following formula to calculate a confidence interval for a difference in population means: Confidence interval = ( x 1 – x 2 ) +/- t*√((s p 2 /n 1 ) + (s p 2 /n 2 )) where: 2. For example, if you're calculating a 95 percent confidence interval, type =CONFIDENCE (0.05, and then click on the cell (or type its code) containing your standard deviation followed by another comma. Formula to calculate confidence interval in excel. In excel there are two confidence interval functions, The confidence interval for a normal distribution (=CONFIDENCE.NORM) Confidence interval when you are using the T’s distribution (=CONFIDENCE.T) The Microsoft Excel formula for the confidence interval is simply: =CONFIDENCE (alpha, standard deviation, size) This means you need to determine three different statistics before you calculate the confidence interval. Tutorial on using Microsoft Excel to determine confidence internals, margin of error, range, max, min and margin of errorPlaylist on Confidence Intervalshttp://www.youtube.com/course?list=EC36B51DB57E3A3E8ERelated Videos:How to Read A Normalized Table (for z scores).http://www.youtube.com/watch?v=dWu0KLXuEpALike MyBookSucks on: http://www.facebook.com/PartyMoreStudyLessLike us on: http://www.facebook.com/PartyMoreStudyLessDavid Longstreet Professor of the UniverseProfessor of the Universe: David Longstreet http://www.linkedin.com/in/davidlongstreet/MyBookSucks.Com How to use Excel to Calculate Confidence Interval - YouTube In turn, the confidence value is used to calculate the confidence interval (or CI) of the true mean (or average) of a population. Use the Confidence function according to the format in the last section. =CONFIDENCE(alpha,standard_dev,size) The CONFIDENCE function uses the following arguments: 1. Size (required argument) – This is the sample size. So, a significance level of 0.05 is equal to a 95% confidence level. It’s a way to represent the uncertainty of your data in a scientific way. 3. The significance level is equal to 1– confidence level.