Level of evidence for causality - how to find causal relationship

Welcome to the first article in our series of introductions to causal inference! Today, we'll dive into the fascinating world of evidence levels for causality. Have you ever wondered how researchers establish a causal relationship between two variables? Let's explore the various methods they use to determine the level of evidence for causality.

Meta-Analysis: Unlocking the Power of Combined Studies

Meta-analysis is like a superhero team-up of scientific studies. It involves combining and analyzing data from multiple studies on the same topic to draw a more robust conclusion. By synthesizing the results of various studies, researchers can uncover patterns and trends that may not be evident in individual studies alone. Think of it as harnessing the collective power of many studies to gain a deeper understanding of cause and effect.

• Pro: Meta-Analysis is something like collecting lots of experiment results and concluding the results.
• Con: It needs more experiments before meta-analysis.

Statistical Experiments: Unleashing the Power of Randomness

Statistical experiments allow researchers to establish causality through controlled and randomized studies. They involve manipulating one variable while keeping all other factors constant. By randomly assigning participants to different groups, researchers can compare the outcomes and determine whether the manipulated variable indeed caused a change. These experiments are often conducted in laboratories and are crucial in establishing causal relationships. For example, AB testing, experiment design in manufacturing, and clinical trial in healthcare industry.

• Pro: Experiment is a golden rule for causality.
• Con: It faces lots of problems, such as time, cost, ethical, etc.

Quasi-Experiment: A Sneaky Approach to Causality

Sometimes, conducting a traditional experiment is impractical or unethical. That's where quasi-experiments come into play. These studies share similarities with traditional experiments, but they lack random assignment of participants. Quasi-experiments make use of naturally occurring situations or pre-existing groups to compare outcomes. While they may not provide the same level of evidence as a randomized experiment, they can still offer valuable insights into causality. For example, RDD, DID, synthetic control.

• Pro: We can save time and cost when conducting experiments.
• Con: The data under certain scenarios can be used in this kind of methods.

Counterfactuals: Imagining a Different Reality

Have you ever wondered what would have happened if things unfolded differently? Counterfactuals allow us to explore that very question. In causal inference, counterfactuals involve comparing what actually occurred with what would have happened if the causal variable had a different value. By analyzing the differences between these two scenarios, researchers can determine the causal impact of the variable. Counterfactual reasoning is a powerful tool in causal inference, especially when direct experimentation is not feasible.

• Pro: It can use machine learning, deep learning, or any models you want.
• Con: It needs lots of assumptions, and some of them are not testable.

Descriptive Statistics: Unveiling Associations

Descriptive statistics provide us with a way to summarize and analyze data. While they don't establish causality directly, they play a crucial role in identifying associations between variables. Researchers use descriptive statistics to measure the strength and direction of relationships, providing initial insights into potential causal links. However, it's important to remember that correlation does not imply causation. Further investigation using other methods is often needed to establish a causal relationship.

• Pro: Easy
• Con: It only find association, not causality.

When we cannot conduct experiments to establish causal relationships, causal inference steps in as a valuable tool. It allows us to draw conclusions about causality by analyzing various methods discussed earlier. Causal inference enables researchers to uncover insights and make informed decisions even in situations where conducting experiments may be impractical or impossible.

This is just the first article in our series of introductions to causal inference. In the upcoming articles, we will delve deeper into these methods, explore real-life examples, and uncover the exciting world of causal reasoning. So stay tuned, as we embark on a journey to unravel the mysteries of causality!