Consider: A coin is tossed 50 times, what is the probability of getting 30 heads? What is the probability of getting at least 30 heads? Example: Calculate the probability that in 75 rolls of a single die, a five will appear between 10 and 20 times (inclusive). n = p = x Step 1: Check to see if the normal approximation can be used. Step 2: Calculate the mean and the standard deviation. Step 3: Find the z-­‐score relating to the appropriate values. Step 4: Find the corresponding z-­‐values using the table. Step 5: Determine the probability. Example: A bank found that 24% of its loans to new small businesses become delinquent. If 200 small businesses are selected randomly from the bank’s files, what is the probability that at least 60 of them are delinquent? Example: A multiple choice test has 20 questions. Each question has 4 possible answers. Find the probability that a student who guesses the answer for each question will get: a) exactly 15 correct b) between 1 and 10 answers correct.