If I take what the other person played the last round into account, then I have a better chance at winning in the next round compared to playing at random.

In my research I found that “If a player loses a round by offering up a “rock” they are more likely to play “paper” the next time. If a player wins a round with the “rock” hand, it’s more likely that they will play “rock” again. It’s the “Win-stay, lose-shift” theory, which suggests that people tend to stick with a winning strategy and change strategies after losing.”¹ After losing, people are more likely to use the play that would’ve won against what they just played. For example, in the scenario above, the player that first offered up rock got beat by paper, so then they are more likely to play paper because that is what would’ve beaten what they just played. This means that as an opponent, the best play would be scissors.

Controlled Variables: How many games of "Rock, Paper, Scissors" played with a strategy or without a strategy. Also only one person can use the strategy, and that was me.

Independant variable: The use of a strategy to win more games of "Rock, Paper, Scissors" where each game consists of 3 rounds.

Dependant variable: The result (win, loss or draw) of each round played and the outcome (win, loss or draw) of each game.

I played 10 best of 3 games (30 single rounds) of RPS against both my mom and my sister without using any strategy of how to win more in RPS and saw my winning average/percent. Then I played another 10 best of 3 games using the strategy in RPS against my mom and my sister. After finishing, I compared my results to see if I had improved my win ratio with a strategy.

During the games I observed that when I used the strategy against my opponents who were playing randomly the frequency of my wins increased.

After I completed the experiment I calculated the percantage of my wins and compared using a strategy versus not using a strategy. Here are my findings:

Experiment Test #1 (No strategy)

My overall game result

Average: Win: 3/10, lose: 2/10, draw: 5/10

Percent: Win: 30%, lose: 20%, draw: 50%

Experiment Test #1 (Strategy)

My overall game result

Average: Win: 4/10, lose: 2/10, draw: 4/10

Percent: Win: 40%, lose: 20%, draw: 40%

Experiment Test #2 (No strategy)

My overall game result

Average: Win: 3/10, lose: 1/10, draw: 6/10

Percent: Win: 30%, lose: 10%, draw: 60%

Experiment Test #2 (Strategy)

My overall game result

Average: Win: 6/10, lose: 3/10, draw: 1/10

Percent: Win: 60%, lose: 30%, draw: 10%

In conclusion, the results of my winning statistics in both experiments suggest that my hypothesis was right. When you use the “Win-stay, lose-shift” strategy in RPS to base your plays in best of 3 games, there is a higher chance of winning!

The way you could use this strategy in a real life situation is that, if for example, you are in a argument, you can try to settle it with rock-paper-scissors knowing that if you use this strategy, there is a high probaility that you will win.

One source of error is that rock-paper-scissors is a game of chance, and you will never get a strategy that is a 100% guaranteed win, there will always be a chance that you will not win even by using the strategy.  Another source of error could be that unknowing to you the person you are playing against knows the strategy as well and this lowers the probability that you will win the game.

1. https://www.huffpost.com/entry/rock-paper-scissors_n_5255288

Rock Paper Scissors Study Reveals Sneaky Formula For Winning The Game | By: Jacqueline Howard

2. https://www.youtube.com/watch?v=UBuH1b0Dqm0&t=379s

1st Place Science Fair Ideas - 10 Ideas and Tricks to WIN! | By: Mark Rober

3. https://www.nationaldaycalendar.com/international/world-rock-paper-scissors-day-august-27#:~:text=Rock%20Paper%20Scissors%20is%20considered,this%20game%20in%20Japanese%20history 

World Rock Paper Scissors Day | By: National Day Calendar

4. https://wrpsa.com/the-rise-and-triumph-of-the-most-celebrated-rock-paper-scissors-players-of-all-time/#:~:text=In%202009%2C%20he%20set%20the,Rock%20Paper%20Scissors%20training%20techniques

The Rise and Triumph of the Most Celebrated Rock Paper Scissors Players of All Time | By: Clever Canuck

5. https://www.pgpedia.com/r/rock-paper-scissors#:~:text=The%20rock%20is%20a%20closed,and%20scissors%20wins%20against%20paper 

Rock-Paper-Scissors | By: Play and Playground Encyclopedia

I would like to thank my sister and my mom for helping me with this project and taking the time out of their day to play multiple rounds of rock-paper-scissors against me, even when I made mistakes and had to do the games over. I would also like to thank my school for nominating me to join the Calgary Youth Science Fair.