You are told that the weights of bags of almonds are normally distributed with a mean of 250 grams and a standard deviation of 4.29 grams. Floor managers take random samples of bags to check that they are filled correctly. A random sample of 19 bags had an average weight of 255.92 grams with a standard deviation of 12.74 grams. From the information supplied, what is the value that is represented by the symbol s?

Please do NOT give units with your answer. Please give your answer correctly rounded to two decimal places.