Proving My Toddler Really Doesn’t Know her Left Foot from her Right

Minitab Blog Editor 05 May, 2014

"Do it myself!

If only I had a nickel for every time I heard that phrase from my toddler in a given day. From throwing away trash, to putting frozen waffles in the toaster, to feeding the dog, I hear it so often that I could possibly retire with all the nickels I’d collect.

And of course, I hear this proclamation every single time my 2-year-old puts on her shoes.

What happens when a toddler tries to put on their own shoes? Well, at least in the case of my little one, the left shoe goes on the right foot, and the right shoe on the left foot, followed by a triumphant “Do it myself! Yay!!!” And the occasional round of clapping.

Watching this everyday exercise in toddler independence got me thinking—is she randomly picking her left foot versus her right, which any kid has a 50/50 chance of doing? Or, does she really think that the right shoe goes on her left foot and vice-versa?

Since I have plenty of time on my hands while I watch her struggle with her shoes, I decided to collect some data.

The 1 Proportion Test

For the next 25 times she tried on her shoes, I tallied how many times she did it correctly and incorrectly. Since my daughter has an affinity for shoes that would give even Imelda Marcos a run for her money, it fortunately didn’t take me long to collect 25 points of data.

Out of the 25 times she put on her shoes, she did it incorrectly 19 times. So, is this 76% failure rate just due to random chance? Or is 19 out of 25 significantly worse than a random 50/50 chance?

I turned to Minitab Statistical Software and the 1 Proportion Test to find out.

Using Stat > Basic Statistics > 1 Proportion, I arrived at the following results:






The 1 Proportion Test answers the question, “If the true population proportion is equal to 50%, how likely is it to see a sample proportion of 76%?” The answer is given as the p-value, which for this dataset is 0.007. That’s not very likely.

Using an alpha level of 0.05, this p-value is statistically significant (since it’s less than 0.05). I therefore can conclude that my toddler’s failure rate is significantly worse than 50%. And perhaps she really does think that her right shoe goes on her left foot.

Practical Significance

While she may not qualify for Mensa just yet, at least I get a good laugh from the gleeful “Yay!!!” I hear every time she gets her shoes on, whether or not they end up where they’re supposed to be.