Descriptive statistics

What is meant by desciptive statistics?

The use of graphs, tables and summary statistics to identify trends and analyse sets of data.

What is meant by measures of central tendency?

The general term for any measure of the average value in a set of data?

What do measures of central tendency include?

The mean, median and mode.

What is the mean?

The arithmetic average.

How is the mean calculated?

By adding up all the values in a set of data and diving by the number of vales there are.

What are the strengths of the mean?

• The most sensitive - includes all the values of the data set within its calculation.

• More representatove of the data as a whole.

What are the limitations of the mean?

• Easily distored by mean scores.

When is most appropriate to use the mean?

When there are no extreme values.

What is the median?

The central value un a set of data when values are arranged from lowest to highest.

What are the strengths of the median?

• Easily identified.

• Unaffected by extreme scores.

• Easy to calculate.

What are the limitations of the median?

• Not all scores are included.

• Less representative.

When is it most appropriate to use the median?

When dealing with wode ranges and extreme values.

What is the mode?

The most frequently occuring value in a set of data.

What is it called when there are two modes?

Bi-modal.

What are the strengths of the mode?

• Easy to caluculate.

• Useful when data is in categories.

What are the limitations of the mode?

• Not useful when there are many modes.

• Not representatove of the data as a whole - overly simple.

When is is most appropriate to use the mode?

With categories.

What is meant by measures of dispersion?

How far scores vary and differ from one another.

What do measures of dispersion include?

The range and standard deviation.

What is range?

A simple calculation of the spread of scores.

How is the range calculated?

Taking the lowest value from the highest value and (usually) adding one.

Why is 1 added to the range?

It is a matematical correctcion that allows for the fact that raw scores are often rounded when they are recorded for research.

What are the strengths of the range?

• Easy to calculate.

What are the limitations of the range?

• Only takes into account the two most extreme values - may be unrepresentative of the data set as a whole.

When is it most appropriate to use the range?

To describe the set of data.

What is standard deviation?

A single value that tells us how far scores deviate from the mean.

What does a large standard deviation indicate?

A greater spread between the data.

What does a low standard deviation indicate?

Data that is more tightly clustered.

What are the strengths of standard deviation?

• More precise than the range.

• Includes all values in the final calculation.

What are the limitations of standard deviation?

• Can be distorted by extreme values.