Range, IQR, and standard deviation

What this quiz covers

Range, IQR, and standard deviation are the core tools for describing variability, and this quiz helps you use them correctly in real data situations.

Every question is multiple-choice with 4 options and no timer, so you can focus on accuracy and reasoning rather than speed.

Skills you’ll practice

You’ll practice calculating range and IQR from raw data or a five-number summary, and interpreting what each value says about spread.

Standard deviation items mix computation sense (what changes SD) with interpretation (how tightly values cluster around the mean).

Common pitfalls to avoid

• Mixing up IQR (Q3 − Q1) with the full range (max − min)
• Forgetting to sort data before finding quartiles
• Using the wrong quartile method when a prompt specifies a convention
• Treating standard deviation as “average value” instead of “typical distance from the mean”
• Ignoring outliers when choosing between IQR and standard deviation

Difficulty and question settings

Difficulty is balanced: easier questions build confidence with definitions and basic calculations, while harder ones test interpretation, outliers, and choosing the best spread measure.

Before you start, choose your question count and difficulty to match your goal - short sets for quick review, or longer runs to build consistency across mixed problem types.