Descriptive statistics -Measures of central tendency and measures of dispersion Flashcards
What are descriptive statistics
A describe the data and show as general patterns and trends
There are two main ways to summarise data what are they?
Measures of central tendency and measures of dispersion
What is a conclusion?
A conclusion succinctly describes the findings of a study
What are inferential statistics?
Where you make an inference from the conclusions based on the participants in your study and extend it to all people
What are measures of central tendency?
they inform us about central or middle values for a set of data – they are averages
An average can be calculated in three different ways - what are they?
The mean, median mode
How is the mean calculated?
By adding up all the numbers and dividing by the number of numbers
How is the median calculated?
The median is the middle of value in an ordered list
How is the mode calculated?
Mode is a value that is most common
What are the strengths of the mean?
It makes use of the values of all the data
What are the strengths of the median
It is not affected by extreme scores
What are the strengths of the mode?
It is useful when the data are in categories
What are the weaknesses of the mean
It can be unrepresentative of the numbers if there are extreme values
What are the weaknesses of the median?
Not as sensitive as the mean because not all values are reflected in the median
What other weaknesses of the mode?
Not a useful way of describing data when there are several nodes
What is the top tip when dealing with this typical exam question: identify a suitable method of central tendency to use with the results from this study and explain why you would choose the method
Look to see if there are any extreme values in the dataset given and if there are then the median is best
What are measures of dispersion?
A set of data can be described in terms of how dispersed or spread out the numbers
What is a range?
The range is difference between the highest and lowest number
What is standard deviation?
This is a measure of the spread of the data around the mean
What are the two main ways of measuring dispersion?
The range and standard deviation
Why would we use standard deviation rather than the range
Standard deviation is a more precise method of expressing dispersion
What are the strengths of the range?
It is easy to calculate and it provides you with direct information without having to do many calculations
What are the weaknesses of the range?
It can be affected by extreme values and it doesn’t take into account the number of observations in the data set
What are the strengths of standard deviation?
It is a more precise measure of dispersion because all values are taken into account
What other weaknesses of standard deviation?
It is unduly affected by extreme values which increase the standard deviation and make it less representative of the dataset
