Using the applet, explore the results for simulating a group of 30 people and noting whether there is a duplicated birthday (whether at least two people have a matching birthday).  Run 20 trials. 

How many of your 20 trials had at least two people with the same birthday (i.e., how many trials had duplicates)?

What is the relative frequency of trials that had at least two people with the same birthday? (This is your estimated probability of at least one birthday duplicated in a group of 30 people.)