do i use number of observation or df for this?Constructing a 95% confidence interval estimate: In Excel, you can use the CONFIDENCE.NORM function to calculate the confidence interval. The syntax is CONFIDENCE.NORM(alpha, standard_dev, size). Here, alpha is 0.05 (for a 95% confidence level), standard_dev is the standard error from your regression output (0.750), and size is the number of observations (100). The result is the margin of error, which you would add and subtract from your predicted mean to get the confidence interval