TRUST Research Center

🍎🍊 “We can’t compare apples to oranges. Or May be we can!!!"

Propensity Score Matching (PSM)
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⚠️ **The core problem: Selection Bias**

In real-world studies, treatment groups are often different *before treatment even starts.*

Example:

💊 New treatment group → younger, lower-risk patients
🏥 Standard treatment group → older, sicker patients

So if outcomes differ later…
❌ it may NOT be because of the treatment itself.

This is the classic:

🍎 **Apples vs Oranges problem**

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🎯 **What PSM tries to do**

PSM creates *fairer comparisons* by matching patients with similar baseline characteristics.

Think of it as:

🧍‍♂️ Matching each treated patient
with
🧍‍♀️ a similar control patient

based on:
✔ age
✔ s*x
✔ comorbidities
✔ disease severity
✔ other baseline variables

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📌 **The 4-step idea behind PSM**

1️⃣ Collect baseline characteristics
2️⃣ Calculate a “propensity score”
→ probability of receiving the treatment

3️⃣ Match patients with similar scores
4️⃣ Compare balanced groups

⚖️ After matching, groups become more comparable → less biased analysis

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💡 Important insight:

PSM does **NOT** create perfect randomization.

It only balances:
✔ measured variables

But:
❌ hidden or unmeasured confounders may still exist

That’s why:
🧪 RCTs remain the gold standard
📊 But PSM greatly improves observational studies

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📌 Bottom line:

Without adjustment:
🍎 ≠ 🍊

With proper matching:
🍎 🤝 🍊

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To learn more about observational studies and PSM, join our upcoming course

👉 https://wa.me/201119678899?text=I%20want%20to%20join%20the%20observationa%20studies%20course

Observational study designs made simple 👇

This infographic breaks down the core analytical designs:
🔹 Case-Control → looking from present to past
🔹 Cohort → following from present to future
🔹 Cross-Sectional → a snapshot at one point in time
🔹 Hybrid designs (Nested case-control & Case-crossover)

💡 Each design serves a different purpose — choosing the right one is critical for generating valid evidence.

If you work with real-world data or are planning a research project, understanding these designs is essential.

📩 Want to learn how to choose and apply the right design with confidence? click on the following link

👉 https://wa.me/201119678899?text=I%20want%20to%20join%20the%20Observational%20Studies%20course