Inferential Statistics • Lesson 7

Point Estimation

Learn how a sample can be used to estimate an unknown population parameter with a single numerical value.

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Concept 1PARAM VS STAT

Parameter vs Statistic

A parameter is a number that describes an entire population — usually unknown. A statistic is a number computed from a sample. Point estimation uses a statistic to estimate a parameter.

Learn by seeing

Population vs sample quantities

Population → Parameter (μ, p, σ²)   usually unknown
Sample     → Statistic (x̄, p̂, s²)   what you compute

The parameter is the target; the statistic is the evidence.

Population

μ

Parameter · unknown

Sample

x̄

Statistic · computed

Analyst mindset

Ask the right question

1. What is the population?

Identify the complete group you want to understand.

2. What sample do we have?

Determine which observations are actually available.

3. Which statistic estimates the parameter?

Use the sample statistic as the point estimate.

Lesson summary

Remember these ideas

Parameter

Describes the population.

Statistic

Is calculated from the sample.

Point estimate

Uses one number to estimate a parameter.

Sample mean

Estimates the population mean.

Sample proportion

Estimates the population proportion.

Bias

Represents systematic estimation error.

Interval estimate

Provides a range instead of one value.