Statistics

Question 1

What is the median?

Accepted Answer

The middle value when the data is arranged in order. If there is an even number of values, it is the average of the two middle ones.

Question 2

Why do we use the median sometimes instead of the mean?

Accepted Answer

The median is not affected by very large or very small extreme values (outliers), so it can better represent the 'typical' value.

Question 3

In a frequency table, what does the entry 'below 40: 24' in a cumulative column mean?

Accepted Answer

24 people have values less than 40. Cumulative frequencies show the position of the last person in each class when everyone is lined up in order.

Question 4

A grouped table has 35 people. Cumulative frequencies: below 20: 8, below 30: 15, below 40: 24. In which class is the median?

Accepted Answer

Median is the 18th person. Below 30 covers up to the 15th and below 40 up to the 24th, so the median is in the class 30–40.

Question 5

In the textbook method for grouped median, what two assumptions do we make about the people in a class?

Accepted Answer

(1) The class is split into as many equal parts as there are people, one person per part. (2) Each person's value is the midvalue of their part.

Sample questions