Descriptive statistics Flashcards
Define Categorical data
Has 2 or more categories with no ordering to them (usually binary or nominal)
Define discrete data
Has a fixed value with a logical order (usually ordinal, ratio, or interval variables)
Define continuous data
Can take any fractional value (usually ratio or interval variables)
How can frequencies be presented?
As its raw frequency or as a percentage frequency
Define Mode
The score occurring most often in a dataset
Define Median
The middle score in a dataset
Define Mean
Sum of data point divided by number of data points
Define Central tendency
Where the centre of our frequency distribution lies
Which bar on a bar chart would be the mode?
The highest bar
How would you work out the median in an odd value dataset?
(n+1)/ 2
How would you work out the median in an even value dataset?
Middle two values/ 2
What are some pros of the median?
Insensitive to outliers, often gives a real data value and is useful for ordinal data
What are some cons of the median?
Ignores a lot of the data, difficult to calculate without a computer and can’t be used with nominal data
What are some pros of the mean?
Uses all of the data, is most effective for normally distributed datasets
What are some cons of the mean?
Sensitive to outliers, values are not always meaningful and is only useful for ratio and interval data
What are the measures of spread for the mode?
There are no measures of spread
What are the measures of spread for the median?
‘distance-based’ measures e.g. range and interquartile range
What are the measures of spread for the mean?
‘centre-based’ measures of spread e.g. variance and standard deviation
Define the interquartile range
Ignores most extreme values and is the range of scores within the middle 50% of scores
Define the Lower quartile range
Median of lower half of data
Define the Upper quartile range
Median of upper half of the data
What are the pros and cons identical to?
The median pros and cons
Define Deviance
Take each score and subtract it from the mean
Define squared errors
Take each deviance score and square it
Define the variance
Average squared errors
What are the pros of variance?
Uses all of the data and forms the basis of several other tests
What are the cons of variance?
Requires a normal distribution and is sensitive to outliers
Define Standard deviation
A measure of spread that’s equal to the unit of measurement of the dependent variable
How would you calculate the Standard deviation?
Using the square root of variance
What does the Standard deviation allow us to do?
Get an unbiased estimate of the population’s standard deviation if we only have access to a sample of data
What can Standard deviance estimate?
Population based on a sample
