What is Statistics?

Statistics is the science of learning from data. It provides methods to collect data, summarize it, and draw reliable conclusions under uncertainty.

Why do we need statistics?

In real life, we rarely see the full truth. We see samples, partial information, and noisy measurements. Statistics helps us make decisions using evidence rather than intuition alone.

Two major parts of statistics

1) Descriptive statistics

Descriptive statistics summarizes data. Examples include averages, percentages, charts, and measures of spread such as the standard deviation.

2) Inferential statistics

Inferential statistics uses a sample to make conclusions about a larger population. Examples include confidence intervals, hypothesis testing, and regression models.

Key words you will see often

Population: the full group you care about (e.g., all patients in a hospital).
Sample: the observed part of the population (e.g., 200 patients).
Variable: a measured property (e.g., age, blood pressure, income).
Parameter: a true population value (usually unknown), like the real mean.
Statistic: a sample-based value, like the sample mean.

Simple real-world examples

Example A: Surveys

You want to know what percentage of students are satisfied with a course. You cannot ask everyone, so you take a sample and estimate the percentage, including uncertainty.

Example B: Medical research

You compare two treatments and ask: is the difference real, or could it be random variation? Statistics provides the framework to answer this scientifically.

Example C: Business decisions

A company tests two marketing messages. Data shows one performs better, but statistics helps confirm whether the improvement is meaningful or just noise.

What you will learn next

Types of data (categorical vs numerical)
Mean, median, variance, and standard deviation
Probability basics and distributions
Confidence intervals and hypothesis testing
Regression and interpretation

Next lesson: Types of Data (coming soon).

EasyStatisticsAcademy — simple statistics with practical software-based examples.