In the full lesson
- When n < 30 (text)
- Visualizing the CLT (example)
- Practical Advice (tip)
Open the Sampling & CLT lessons or see what Premium includes.
Module 4 · Sampling & CLT · Topic 7
CLT and Sample Size
The n ≥ 30 Guideline. The “n ≥ 30” rule is a convenient guideline, not a strict law. The required sample size depends on the population’s shape: symmetric populations need fewer observations, while heavily skewed or multimodal populations need more.
This is the opening of a Premium lesson. The full lesson, with its 4 sections, reads in the interactive course; the module's first lesson is free.
Key formulas
From the Sampling & CLT formula sheet
- Standard Error of xbar:
SE_xbar = sigma / sqrt(n)- Standard deviation of the sampling distribution of the sample mean.
Related glossary terms
- Parameter: A number that describes an entire population. Example: The true mean height of all students at a university.
- Statistic: A number computed from a sample. Example: The mean height of 80 sampled students.
- Standard Error: The standard deviation of a statistic across repeated samples. Example: The standard error of xbar is sigma divided by sqrt(n).
Go interactive
Work this topic in StatRise
This module opens on its first lesson free; the rest of it unlocks with Premium. Every calculator and simulation below is free.
Keep reading