To find margin of error for confidence interval with sample means ( unknown) on Excel: =CONFIDENCE.T(alpha, standard deviation, sample size) Example 3: Wildlife conservationists studying grizzly bears in the United States found that the mean weight of 25 adult male grizzly bears was 600 pounds with a standard deviation of 90 pounds. Construct and interpret a 98% confidence interval for the mean weight of all adult male grizzly bears in the United States. Assume that the weights of all adult male grizzly bears in the United States are normally distributed.