Perform 50,000 experiments with 365 days per year and vary the number of people from 2 to 100. 50,000 runs with 365 days, and 2 people, 50,000 runs with 365 days and 3 people, ... 50,000 runs with 365 days and 100 people. Total of 4,950,000 runs, 50,000 runs per experiments * 99 experiments = 4,950,000 runs. For each of the given number of people determine the percentage of experiments where at least one pair of people shared a birthday. At what number of people (between 2 and 100) does the percentage first exceed 50%? Does the answer surprise you? How did it compare to your predicted answer?

Include a table in a comment in your CodeCampTester.java program with the results of this experiment using the following format:

Num people: 2, number of experiments with one or more shared birthday: 120, percentage: 0.24
.....
Num people: 100, number of experiments with one or more shared birthday: 50000, percentage: 100.00

At the top of the table state how many people it requires to have a 50% chance of there being at least 1 shared birthday, given a 365 day year.

 

Sorry I am so dumb. I already wrote out the code, but I still can't understand how to get the result of this experiment. : (

public static int sharedBirthdays(int numPeople, int numDaysInYear) {
        // check preconditions
        if (numPeople <= 0 || numDaysInYear <= 0) {
            throw new IllegalArgumentException("Violation of precondition: " +
                    "sharedBirthdays. both parameters must be greater than 0. " +
                    "numPeople: " + numPeople +
                    ", numDaysInYear: " + numDaysInYear);
        }
        int[] birthdays = new int[numPeople];
        Random random = new Random();

        if (numPeople == 1) {
            return 0;
        } else {

                for (int i = 0; i < numPeople; i++) {
                    birthdays[i] = random.nextInt(numDaysInYear);
                }
                int numPairs = 0;
                for (int i = 0; i < numPeople; i++) {
                    for (int j = i + 1; j < numPeople; j++) {
                        if (birthdays[i] == birthdays[j]) {
                            numPairs++;
                        }
                    }
                }
                return numPairs;
            }
        }

    public static void averagePairs(int numPeople, int numDaysInYear, int trails) {
        int pairs = 0;
        for (int i = 0; i < trails; i++) {
            pairs += sharedBirthdays(numPeople,numDaysInYear);
        }
        double average = (double) pairs / (trails * numPeople);
        System.out.printf("The average number of pairs of people with shared birthdays is %.12f"
                , average);
    }