A day care program has an average daily expense of $75.00. The standard deviation is $15.00. The owner takes a sample of 64 bills. What is the probability the mean of his sample will be between $70.00 and $80.00? Step 1. Calculate a z-score for $70.00:
Step 2. Give the probability for step 1:
Step 3. Calculate the z-score for $80.00:
Step 4. Give the probability for step 3:
Step 5. Add the probabilities from steps 1&3: