INTRODUCTION

GET TO KNOW YOUR DATA

HOW TO SELECT A STATISTICAL TEST

TYPES OF STATISTICAL TESTS

“The true method of knowledge is experiment.”

**William Blake**

Observation and experimentation provide us with the clearest view of the world and its machinations. Some early scientists believed in using intuition or logic. But the problem is that our intuition does not always reflect reality.

We can run experiments within the world by manipulating or observing the independent variable, measuring its effects on a dependent measure.

Here is a difficult truth: we are limited by everything that we do not know and biased by what we do know.

We see this every day. A Congressman once **brought in a snowball **to “refute” climate change. A lot of misinformation about the COVID-19 vaccine also relies on similar logic and intuition about “natural immunity”. We need to use proper experimental methods to conclude.

Independent and dependent variables help us measure reality. Often we are interested in seeing how an independent variable, X, might affect a dependent variable, Y.

To do this, we design an experiment where we record or manipulate the independent variable. This independent variable is stable and uninfluenced by other variables. Unless you are a Time Lord of sorts, time is an independent variable.

Another example would involve measuring pollution in the environment as an independent variable, to see its effects on cognition. Here the dependent variable is anything that is observed and potentially impacted by our independent variable. It is the measurement of our experimental outcome.

**Independent variable: **Changed or observed during an experiment to measure its effects on another variable. This variable is not affected by the other variables that you are measuring.

**Dependent variable:** The outcome measure of your experiment. You are testing whether the independent variable influences this variable or outcome. Your independent variable might not explain all the changes, often there are unmeasured extraneous variables that confound your results.

Logic and intuition are unreliable methods for understanding the world. There are often variables we do not know or understand that we can not grasp through simple observation.

When we perform experiments, we can see how one independent variable, that we either manipulate or track, affects our outcome measures. These outcomes or dependent measures will provide us data to run statistical tests.

Then we can see whether the independent variable explains the changes in the dependent variable or if extraneous variables are influencing the results.

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