Measures of Dispersion Flashcards
What are the two measures of dispersion?
The range and standard deviation
How do you calculate the range?
By subtracting the lowest score from the highest
What are two strengths of the range?
It’s quick and easy and can be used with rating or fixed data
What are two limitations of the range?
It doesn’t take into account individual values and it can be seriously affected by extreme scores
What is standard deviation?
It measures the average spread around the mean
What does a large standard deviation tell us?
The spread of scores is wide
What does a small standard deviation tell us?
All of the scores are clustered together around the mean
How do you work out the standard deviation?
You work out the difference between the mean and each score. You then add the differences together and divide it by the number of scores
What are two strengths of standard deviation?
It uses all of the scores and it allows interpretation of individual scores
What are two limitations of standard deviation?
It is time consuming and it is less meaningful if the data is not normally distributed
