Descriptive Statistics 🔢 Flashcards
What are descriptive statistics?
Once quantitative data has been collected, it is important to summarise this data numerically.
— This quantitative summary is called descriptive statistics (allows to view data as a whole)
It also helps the reader to get an understanding of the data and saves them from needing to navigate through lots of results to get a basic understanding of the data.
Descriptive statistics include a measure of central tendency and measure of dispersion (which will have been selected based on the type of data collected), and can also include percentages.
What are measures of central tendency?
Measure of central tendency tell us about the central, most typical, value in a data set and are calculated in different ways:
— Mean
— Median
— Mode
What is mean?
Mostly widely used measure of central tendency is the mean.
The mean = the ‘average’
The mean is calculated by adding all of the data together, and dividing the sum by how many values there are in total.
— The value that is then given should be the value that lies somewhere between the maximum and mimum values in the data set.
What is median?
In cases where there are extreme values in a data set, it makes it difficult to get a true representation of the data through using the mean, the median can be used instead.
The middle value in the data set.
If there are two middle numbers you add them by together and divide by two.
What is the mode?
This refers to the value or score that appears most frequently within the data set.
— Can be quite misleading of the data set and may not be truly representative.
It is possible that a data set can have more than one mode.
If there are two, then the data set is called bi-modal.
What are measures of dispersion?
Measures of dispersion are descriptive statistics that define the spread of data around a central value (mean or median). There are two measures of dispersion:
1) Range
2) Standard deviation
What is range?
Range is calculated by subtracting the lowest score in the data set from the highest score and adding 1.
What is standard deviation?
A much more informative measure of dispersion is the standard deviation.
The standard deviation looks at how far the score deviates from the mean.
— If the standard deviation is large, this suggests that the data is very dispersed around the mean and participants score very differently.
— If the standard deviation is small, this suggests that the values are very concentrated around the mean, and that everyone scored relatively similarly.
