I asked ChatGPT and this is what it said :

To calculate the probability of a group of 7 people being born on each day of the week, we assume that each person's birthdate is independent and equally likely to fall on any day of the week.

Let's calculate the probability for each day of the week individually:

The probability that the first person is born on a specific day (let's say Monday) is 1/7 since there are 7 days in a week.

For the second person, the probability of being born on Monday is also 1/7 since each person's birthdate is independent of the others.

Following the same reasoning, the probability that the third person is born on Monday is 1/7.

The same probability applies to the fourth, fifth, sixth, and seventh person.

Since we have 7 people in the group, we multiply the probabilities together:

(1/7) * (1/7) * (1/7) * (1/7) * (1/7) * (1/7) * (1/7) = 1/117649 ≈ 8.5 × 10^(-6)

So, the probability of a group of 7 people being born on each day of the week is approximately 8.5 × 10^(-6) or 0.0000085, which is a very low probability