Descriptive Statistics Flashcards
Component 2
What are the 4 levels of measurement?
- Nominal
- Ordinal
- Interval
- Ratio
What is nominal data?
(one bullet point, explanation)
- Categorises and labels variables
Data can be classified into strict categories. Nothing can be in multiple categories
What is ordinal data
(two bullet points, explanation)
- Categories and labels variables
- Ranks categories in order
Data has a rank. Doesn’t have equal intervals between each each unit. Based on subjective opinion
What is interval data?
(three points, explanation)
- Categorises and labels variables
- Ranks categories in order
- Has equal gaps between data
Data measures something on a scale that includes units of equal size
What is ratio data?
(four points, explanation)
- Categorises and labels data
- Ranks categories in order
- Has known, equal variables
- Has a true zero
Data has all the properties of interval data but has a true zero
What are descriptive statistics used to do?
To describe or summarise the characteristics of a sample or data set
What are the measures of central tendency?
- Mean
- Median
- Mode
What are the measures of dispersion?
- Range
- Standard deviation
What are the advantages and disadvantages of the mean?
+ Most sensitive measure as it uses every value in the data set to calculate an average
- Can be easily distorted by extreme values
- Can’t be used with nominal data
What are the advantages and disadvantages of using the median?
+ Not affected by extreme values
+ Appropriate for ordinal data and can be easier to calculate
- Not as sensitive as the mean as the exact values arent used
What are the advantages and disadvantages of using the mode?
+ Unaffected by extreme values and is useful for discrete data
+ Only method that can be used for nominal data
- Not useful when there are several modes like in interval or ratio data
What are the advantages and disadvantages of using the range?
+ Identifies how spread out the data is
- Is affected by extreme values
- Doesn’t indicates whether the data is closely grouped to the mean or spread evenly
What is the method of finding the standard deviation
- Work out the mean for the data set
- Subtract the mean from each data point
- Square the result
- Add these up
- Divide by n-1
- Finally, calculate the square root
What are the advantages and disadvantages of using the standard deviation?
+ Precise measure because all the data values are used so can see the spread of data
+ Not as affected by extreme values because it doesn’t just look at the highest and lowest value in a data set
- It can hide characteristics of the data like extreme values because it indicates how far each value is rather than looking at each end of the data set
What does a greater SD mean?
A greater spread of data
What does a smaller SD mean?
Data values are clustered around the mean/ shorter spread of data
