In **problem 1**,

the solution to **number of people** needed such that **probability of 2 people having same birthday comes** out to be **254**.

But **in class** the way it was solved it came out as **23**.

**What am I understanding incorrectly here?**

In **problem 1**,

the solution to **number of people** needed such that **probability of 2 people having same birthday comes** out to be **254**.

But **in class** the way it was solved it came out as **23**.

**What am I understanding incorrectly here?**

1 Like

**Kindly verify** this.

Okay **I think what I misunderstood** is:

In the **class**-

We found that if we have 23 people then there is >50% chance that atleast 2 people have same birthday.

We tried finding probability that **NO ONE has same birthday among themselves**.

In **lab problem 1**-

The situation of interest is that **NO ONE has birthday as that of one specific student**. **BUT** there **may be 2 people** who have **same birthday** (just not same as the one specific student).

**Ex**. If bday of *specific student is 1 March* then *no other student has birthday on 1 March* **BUT** there *maybe 2 students who have birthday of (say) 1 Jan*.

1 Like

I also was somewhat confused by this, but but to make the lab problem_1 to match the lecture one would need to change it to problem_1_1

```
# before
def problem_1(n_students):
# Predefine a specific birthday
predef_bday = np.random.randint(0, 365)
# Generate birthdays for every student
gen_bdays = np.random.randint(0, 365, (n_students))
# print(predef_bday in gen_bdays, predef_bday, gen_bdays)
# Check if predefined bday is among students
return predef_bday in gen_bdays
# after
def problem_1_1(n_students):
# This is no longer relevant as we are looking at any two people and not one specific person
# # Predefine a specific birthday
# predef_bday = np.random.randint(0, 365)
# Generate birthdays for every student
gen_bdays = np.random.randint(0, 365, (n_students))
# check if any two people have same birthday
return len(gen_bdays) - len(np.unique(gen_bdays))
```