A coffee shop surveyed three groups of 5 customers to find out how many cups of coffee the customers drink in one day. The table shows the results of the three samples.
Group 1 {1, 3, 2, 2, 4}
Group 2 {4, 1, 3, 2, 1}
Group 3 {5, 4, 6, 4, 6}
Identify any surveys that are likely biased. Based on the unbiased surveys, estimate the mean number of cups of coffee the customers drink in one day.
Enter your answer in the box. Round to the nearest whole number.