i got it. (24+26+29+31+33+37)/6=180/6 =30. 6 is the number of datas given. thank you Smaug!
You've found the mean of the dataset, not the standard deviation. Standard deviation is sqrt(variance), and variance is "mean of the squared data, minus the square of the mean".
You've found the mean of the dataset, not the standard deviation. Standard deviation is sqrt(variance), and variance is "mean of the squared data, minus the square of the mean".