how do I do this in excel given the regression anaylisi Calculate the margin of error for the 95% prediction interval: This step involves a bit of statistics. You'll need to use the T.INV function in Excel to get the t-value associated with a 95% confidence level and your degrees of freedom (which is your number of data points minus 2). You'll multiply this t-value by your standard error and a correction factor based on your number of data points and the specific X value you're predicting for