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Recency bias: The silent saboteur in statistics

Fri May 19 2023

Jack Virag

Editor in Chief, Statsig

Heads up: No number-crunching abilities are required to grasp this post.

If you have a fear of algebraic symbols, your secret is safe with me.

Recency bias: This fancy term has been all over the psychology and behavioral economics world, but it also sneaks its way into statistics and data analysis, stealthily skewing our interpretation of patterns and trends. Sounds intriguing, right? Stick around to learn more (and not a single standard deviation will be harmed in the process).

Understanding recency bias

First things first. What is this so-called recency bias? Let's break it down:

  1. You take a string of events or a data set.

  2. You focus more on the most recent occurrences rather than older ones.

  3. And voila, you've been hit by recency bias!

In essence, this bias makes us pay more attention to recent information and downplay the importance of older data.

Recency bias in statistics

Recency bias can stealthily sneak into statistical analysis and prediction models, causing analysts to overemphasize recent data while neglecting the historic context. "But I'm an analyst, not a historian," you might protest. Hold that thought.

Imagine you're a financial analyst, and you've been handed the Herculean task of predicting the future performance of a stock. You could:

  • Option A: Look at the entire history of the stock and take an average.

  • Option B: Put a larger weight on the most recent performance of the stock and base your prediction on that.

Given our predisposition to recency bias, you might be tempted to choose option B. After all, what happened 10 years ago seems as relevant as last year's TikTok dances, right?

The perils of overlooking the past

By only considering recent data, we risk drawing conclusions that are not representative of the broader picture. To put it simply, imagine you're only focusing on the last ten minutes of a movie and then writing a full-blown review. That's not fair to the first 110 minutes.

Similarly, if we're looking at a stock that has been bullish (that's Wall Street speak for "going up") in the past week, it doesn't necessarily mean it's going to shoot up tomorrow, next week, or next year. If we consider the entire historical data, we might notice that this stock actually has a history of volatile spikes followed by sharp falls.

Therefore, by succumbing to recency bias, we might end up making predictions that are as off-target as a stormtrooper's aim (Star Wars fans, I see you).

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Escaping the clutches of recency bias

So, how do we break free from this bias? Don't despair. I have some weapons for your analytical arsenal:

  1. Look at the big picture: Before diving into recent data, take a step back and consider the entire data set. Sure, the recent uptick in a stock's price might seem significant, but how does it compare with the historical trends?

  2. Test for statistical significance: This is a fancy way of saying, "check if your results are legit or just a fluke." You don't need to be a statistical wizard for this. Plenty of online tools can do the heavy lifting for you.

  3. Beware of the narrative fallacy: Humans love stories, and we're guilty of molding data to fit our preferred narratives. Be conscious of this and always question the story that you're being sold (or selling yourself).

Recency bias in real life

Alright, let's venture out of the stock market and into the real world. Say you're a digital marketer looking at your website's analytics. You notice a spike in visitors over the last week. Victory dance? Not so fast.

Before you pop the champagne and declare your latest marketing strategy a success, consider this: Is this recent increase in traffic a true reflection of a successful campaign, or is it a temporary blip in your data?

What if the spike was due to a recent public holiday, a viral social media post, or even a mention from an influencer? If you overlook the broader trends and historical data, you may fall into the trap of recency bias and make decisions based on an anomaly rather than consistent performance.

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Wait, there's more!

Fun fact: Recency bias also shows its sneaky face in our day-to-day lives. Can't get over that last season finale cliffhanger? Your binge-watch might have suffered from recency bias.

Or, perhaps you gave a rave review to the latest restaurant you dined in, despite its average food, just because the dessert was out-of-this-world. Yep, that’s recency bias having a field day at the expense of your Yelp review’s credibility.

Recency bias: Conquered!

Now that you know about recency bias and its insidious influence on statistics and decision-making, you're armed and ready to face it head-on. It's all about balance - while recent data may be relevant, it's crucial not to overlook historical data and broader trends.

So the next time you're analyzing a dataset, remember that the road to unbiased analysis is paved with equal consideration of both old and new data. Treat your data points as equal citizens, regardless of their age. Just like in a well-directed movie, every scene has its significance.

And, if you ever feel the urge to give more importance to recent data, understand that this very bias might lead you astray from the path of accurate data analysis. No hard feelings toward recency bias, but it's better left out of our statistical playground.

Feeling empowered? Ready to take on the world of data without the shadow of recency bias looming over your analysis? I thought so. Go forth and conquer, data warrior!

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