Practice · Statistics Quest

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 2 of 3

n or n − 1?

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For each situation, decide which standard deviation is appropriate.

Waiting times of 40 randomly selected patients, used to judge the variability of all patients' waits

Salaries of the 7 members of a board, reported only to describe that board

Fill volumes of 25 bottles taken from a production line to monitor the process

Exam scores of all 30 students in a class, used only to describe that class's results

Blood pressure readings of 120 trial participants, used to draw conclusions about patients in general