Statistics Quest

Practice

Practise until it sticks

Choose a topic, a skill or a difficulty. Calculation exercises have new versions with fresh numbers once you have solved them, so you can practise the method rather than memorise an answer.

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Practice, difficulty 1 of 3

Name the bias

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Classify the main source of bias in each situation.

A ministry estimates internet use with an online questionnaire.
A radio station invites listeners to text in their opinion on a new stadium.
A random sample of 2,000 households is selected, but only 31% complete the questionnaire, mostly older residents.
Employees are asked in a face-to-face interview with their manager whether they plan to leave the company.
A customer survey asks “How much did you enjoy our award-winning service?”
A study of small-business success interviews only firms that are still trading after five years.