Lesson 13: Descriptive Statistics: Measures of Central Tendency and Measures of Dispersion

Question 1

What are measures of central tendency

Answer 1

Measures of central tendency inform us about central values for a set of data. They are ‘averages’ – ways of calculating a typical value for set of data. The average can be calculated in different ways, each one appropriate for a different situation.

Mean
Mode
Median

Question 2

Advantages and disadvantages of mean

Answer 2

Advantage:
The mean is the most accurate measure and it takes into account all the scores.

Disadvantage:
The mean can be distorted by a single extreme value in the set and the mean score may not be one of the actual scores in the set.

Question 3

Advantages and disadvantages of median

Answer 3

Advantage:
The median is unaffected by extreme scores, unlike the mean.

Disadvantage:
The median is not as sensitive as the mean because not all scores are used in the calculation so it can be unrepresentative of the data if the scores are clustered around high and low levels.

Question 4

Advantages and disadvantages of mode

Answer 4

Advantage:
The mode is unaffected by extreme scores.

Disadvantage:
The mode tells us nothing about other scores in the data set.

Question 5

What are methods of dispersion

Answer 5

A set of data can also be described in terms of how dispersed or spread out the data items are.
Range
Standard deviation

Question 6

Advantages and disadvantages of range

Answer 6

Advantage:
The range is quick and easy to calculate compared to standard deviation

Disadvantage:
The range can be easily distorted by extreme values.

Question 7

Advantages and disadvantages of standard deviation

Answer 7

The standard deviation:
It is the average amount that each score differs from the mean.

Advantage:
The standard deviation takes account of all the scores.

Disadvantage:
The standard deviation is more difficult to calculate than the range and can only be used on interval data.