how do you find the critical value for confidence intervals
Note that if you want 95% confidence, you need to enter 0.05. If you want 99% confidence, enter 0.01. If you want to compute confidence intervals using Excel, the critical value of t for a specified number of degrees of freedom (df) and confidence (C, in percent, usually 95) is computed using this formula: TINV (1 â 0.01 * C, DF). The confidence interval of the mean is centered on the sample mean and extends in each direction a distance equal to that critical value of t times the standard error of the mean (SEM).