Task: Question Answering
Input (English): Question: A pediatrician wants to study overweight in children of 14 years, according to the values ​​of the BMI (body mass index). To estimate the necessary sample size, it proposes a confidence level of 95% and a precision of 1 unit of BMI. What other parameters do you need to know to determine the sample size? 
 Options:  <1> The average BMI in the population. <2> The variance of the BMI. <3> The mean and standard deviation of the BMI. <4> The size of the population and the average BMI. <5> The standard deviation of the BMI and the population size.
Output (English): 2