Q:

# 48000 fair dice are rolled independently. Let X count the number of sixes that appear. (a) What type of random variable is X? (b) Write the expression for the probability that between 7500 and 8500 sixes show. That is Pp7500 ď X ď 8500q. (c) The sum you wrote in part b) is ridiculous to evaluate. Instead, approximate the value by a normal distribution and evaluate in terms of the distribution Φpxq " PpNp0, 1q ď xq of a standard normal random variable. (d) Why do you think a normal distribution is a good choice for approximation

Accepted Solution

A:
Answer:1 because almost certain eventStep-by-step explanation:whenever a fair die is rolled the number of getting a 6 is having probability 1/6. Each throw is independent of the otherHence no of sixes would be binomial with p=1/6when 48000 dice are rolled, using binomial would be a hectic task.Hence we approximate to normal distributionX - no of sixes in 48000 throws would be normalwith mean = np = 8000Var =npq = 6666.667Std dev = 81.650Now it is easier to find out$$P(7500<x<8500)\\=P(7499.5<x<8499.5)$$(using continuity correctin)=$$P(|z|<6.1295)\\=1$$we get this probability almost equal to 1d) Normal distribution is a good choice because when no of trials increase using binomial and combination formulae would not be easy