The sum of all X's is 3780. The sum of all X^2 is 80000. The sample N = 180. How can I calculate the variance? Statistics Random Variables Addition Rules for Variances 1 Answer Narad T. Jan 20, 2017 The variance is #=442# Explanation: #sumx=3780# #sumx^2=80000# #n=180# #barx=(sumx)/n=3780/180=21# #V(x)=(sumx^2-barx^2)/180# #=(80000-21^2)/180=79559/180=442# Answer link Related questions If you add two independent random variables, what is the standard deviation of the combined... What is the procedure for calculating the new standard deviation for two combined random... If you multiply each entry of a set by 3 and added 1, how would the mean and standard deviation change? If I know the mean, standard deviation, and size of sample A and sample B, how do I compute the... Can you find the standard deviation of negative numbers? What is the difference between the standard deviation and margin of error? Can a sample have a standard deviation of zero? If you are calculating the standard deviation of measurements, how do you determine how many... Question #d281c A data set has a variance of 0.16. What is the standard deviation of the data set? See all questions in Addition Rules for Variances Impact of this question 7267 views around the world You can reuse this answer Creative Commons License