can you please help me find the right letter (answer) ? it will help me a lot. Thanks in advance

15, Which of the following use the formula of (x) - Ex - p (x]? A. Probability Distribution B. Variance of Discrete Probability Distribution C. Standard Deviation of Discrete Probability Distribution D. Mean or Expected Value of Discrete Probability Distribution 16. If the variance of a probability distribution is 2.6 grams, then what proper way to do to get the standard deviation? A. V26 B. (2.6)- C 161+26 D. 1.61-2.6 17. Which term is calculated by summing the product of the square of the difference between the value of the random variable and the expected value, and the associated probability of the value of the random variable, taken over all of the values of the random variable, and finally taking the square root? A: Probability Distribution B. Variance of Discrete Probability Distribution C. Standard Deviation of Discrete Probability Distribution D. Mean or Expected Value of Discrete Probability Distribution 18. The probabilities that a customer buys 5,8,9,12 and 15 items in a grocery store are 0.06, 0.14, 0.32, 0.28, and 0.20 respectively. Which probability distribution represents the given problem? 12 15 P(X) 0.06 0.14 0.2 0 0.28 0.32 X 5 9 12 15 P(X) 0.32 0.28 0.2 0.14 0.06 C 5 12 15 (X) 0.06 0.14 0.32 0.28 0.2 X 5 12 15 P(X) 0.06 0.14 0.2 0.28 0.32 19. The following table shows the probability distribution of a discrete random variable X. Find the value of n. X 2 P(X) 0.40 0.25 A. 0.15 B. 0.25 C. 0.78 D. 0.35 20, The number of absences from June to March of a student based on his class adviser's record is shown below. If X be the random variable representing the number of absences. Which table represents the probability distribution? Month Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar No. of absences C X 0 1 2 WIN P(X) 2 P(X) 10 10 10 10 10 10 10 10 D O 1 3 W N WN P(X) P(X) 10 10 10 10 10 10 10 10