This is a simple question, our standard deviation represents how spread our data are, and to calculate it we need first to calculate our mean and variance as below:
To calculate our variance, we need to take the difference between each weight and the mean we just calculated and next, we square each difference and final we calculate a new mean with this values as below:
To calculate the standard deviation we just need to make the square root of our variance:
So the final answer is that the standard deviation of the weights of these students is equal to 6.48 or 6.5 (depends on the approximation).
