How would you determine the expected value, variance, and standard deviation of items per purchase?

4) Amy wants to estimate the average number of items per purchase at the express lane of a local grocery store. She has estimated the following probabilities based on a sample size of 50 customers. Determine the expected value, variance, and standard deviation of items per purchase. Items per Purchase Probability 1 0.29 2 0.16 3 0.15 4 0.18 5 0.22