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Let us assume that there are exactly 365 days in a year and that birthdays are uniformly randomly distributed across those days.

First, what is the probability that 2 randomly selected people have different birthdays? The second person's birthday can be any day except the first person's, so the probability is 364/365.

What is the probability that 3 people will all have different birthdays? We already know that there is a 364/365 chance that the first two will have different birthdays. The third person must have a birthday that is different from the first two: the probability of this happening is 363/365. We need to multiply the probabilities since the events are independent; the answer for 3 people is thus 364/365 × 363/365.

You should now be able to solve it for 4 people.

Q: What is the probability that 4 randomly selected people all have different birthdays?

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Non probability sampling is where the samples are not selected randomly.

The answer depends on the demography of the population from which the person is randomly selected.The answer depends on the demography of the population from which the person is randomly selected.The answer depends on the demography of the population from which the person is randomly selected.The answer depends on the demography of the population from which the person is randomly selected.

The answer will depend on what the disease is.

85/500 = 17%

It is approx 0.001824

Related questions

Non probability sampling is where the samples are not selected randomly.

The answer depends on the demography of the population from which the person is randomly selected.The answer depends on the demography of the population from which the person is randomly selected.The answer depends on the demography of the population from which the person is randomly selected.The answer depends on the demography of the population from which the person is randomly selected.

10/12

The answer will depend on what the disease is.

15 19

85/500 = 17%

If the events can be considered independent then the probability is (0.7)4 = 0.24 approx.

It is approx 0.001824

The answer is 0.1586

There is not enough information about the the distribution of the number of people known by each individual - nor the averages. It is therefore no possible to give an answer any more precise than "the probability will be infinitesimally small".

It is 0.73 = 0.343

Using the Poisson approximation, the probability is 0.0418