Types of variable & summarising data Flashcards
What is a variable?
an aspect that can take different values for different participants
What are the two types of variables?
Categorical (dead, alive)
Quantitative (continuous) (numbers)
What is a binary variable?
a variable that only has two categories
What are the 3 types of categorical variables?
Binary
Nominal
Ordinal
What is a nominal variable?
unordered labelled categories (3 or more)
eg blood type: A, B, AB, O
What is a ordinal variable?
small set of ordered categories
eg none, mild, moderate, severe
What are quantitative variables?
values that have quantitative meaning
higher number = more concept eg age
have a large number of potential values eg age, weight
What 2 types of graphical summary can be used to analyse quantitative variables?
Histogram
Box and whisker plot
What are the 5 histogram shapes?
Symmetrical (normal)
Positive skew
Negative skew
Bimodal (2 populations on one graph)
Uniform
When should ‘mean’ & standard deviation be used?
to summarise symmetrical distributions
When should ‘median’ & inter quartile-range be used?
to summarise skewed/asymmetrical distributions
What is distribution of data?
different values that occur and the frequency they occur for a given variable
What are the two ways to summarise distributions?
Numbers (descriptive stats)
Graphs
What are the 2 ways to describe categorical data numerically
Frequency (actual number)
Relative frequency (proportion or percentage of people in a category)
How is categorically data described graphically
using a bar chart where height indicates the number of the category’s
