Why You're Terrible at Being Random (And Don't Even Know It!)

Hello! I'm Siddharth, an ecologist, educator, entrepreneur and parent. I am one of the community leads at Gifted World, and this is the starting of my personal blog corner in this space! I look forward to hearing and learning from you!

If someone asked you to choose a random number between 1 and 100, would you secretly avoid some numbers? Maybe 50 doesn't feel random enough, or perhaps 7 feels especially random!

To explore how people think about randomness, I decided to run an experiment.

The Experiment

On March 21, 2025, I shared a simple form asking people to choose two random numbers between 1 and 100. Within five days, 376 people responded, with another 16 responses arriving later.

But before you read further, pause here! Quickly pick two random numbers between 1 and 100. Write them down and keep them handy—you might discover something surprising about your own choices!

What Numbers Did People Choose?

Let's look at a histogram—a type of graph that shows how many times each number was chosen. The numbers from 1 to 100 are shown along the bottom. Each blue bar shows how often that number was selected, and the red line represents what we'd expect if each number had an equal chance (7.84 times each).

Histogram of the data from the mini-experiment.

Patterns I Predicted:

Here are the patterns I expected people would show:

• Choosing more odd numbers than even numbers.

• Picking prime numbers more frequently.

• Avoiding multiples of 10, because they feel less "random."

• Rarely choosing numbers like 1 and 100.

What Did We Actually Find?

Odd Numbers Win Big!

In theory, odd numbers should be chosen half the time (around 392 times). Instead, people chose odd numbers 485 times—that's about 62%! If you look closely, you can see the graph's jagged "sawtooth" pattern showing how even numbers are neglected.

Multiples of 10 Lose Out!

Multiples of 10 should make up about 10% (78.4 times), but they were chosen only 57 times, about 7%. Clearly, numbers like 10, 20, and 50 don’t feel random enough!

Prime Numbers Are Popular!

There are 25 prime numbers between 1 and 100, meaning we’d expect about 25% of the choices (196 times). Surprisingly, primes were chosen 282 times—that's 36%!

Favourite Numbers Emerge

Some prime numbers were especially popular:

• 7 was chosen 34 times

• 23 was chosen 21 times

• 37 was chosen 18 times

where any single number should only be chosen 8 times if it were truly random.

But even if we remove these favorites, the other primes were still chosen 209 times, much more than we'd expect. Clearly, people feel primes are more "random."

Patterns in Number Pairs

Two curious pattern emerged when looking at pairs of numbers.

People choose numbers in increasing order

If truly random, the second number chosen would be bigger about half the time. Instead, 64% of people chose the second number to be larger than the first!

People choose numbers from 1-10

Only about 4 people (1% of all responses) should have chosen both numbers between 1 - 10. However, we find 50 people (that is, 12.7%, or one-eighth of all respondents) chose both numbers to be less than 10.

So, How Random Were Your Numbers?

Now, look back at your numbers. Did you pick an odd or prime number? Was your second number larger than the first? Or maybe you avoided multiples of 10 without realizing it?

It turns out humans aren’t great at being random—we're influenced by what we believe "feels random." Next time someone asks you to choose a random number, direct them to an actual random number generator, and show them this blog as your justification.

Remember, we can’t judge how random someone's choice is based on just one or two examples. Real patterns only become clear when we look at many responses—hundreds or even thousands, as we've done here! So don't immediately accuse your friend of being biased if they choose 7 as a random number. Instead, gently remind them that large studies (like this one) show clear patterns in how people think about randomness. After all, if no one ever chose 7, wouldn't that be a strange kind of bias, too?

This casual experiment ended up being a very pleasant rabbit hole that I went down! There's also a lot of research around this, which I will bring together in a subsequent blog. Watch this space! Click 'Log In' in the top left corner and create a free member account to be notified about future blogs.

If you want to take a look at the raw data for your own analysis, you can download it from here - https://docs.google.com/spreadsheets/d/1bvIorGOYset93dNsmc9XQ8vroQEh4hwlzyDzhIY3BSw/edit?usp=sharing

If you have any questions or comments, feel free to post it here! I am looking forward to a lively discussion!

If this kind of math and learning excites you, I’m hosting a free online masterclass this Saturday (April 5th) called: Math That Breaks the Internet. We’ll explore the math of going viral — from exponential growth to social media spread to population booms. Please do share it with curious people aged 9 and above