Maths Flashcards
Random sampling
Every item in population has equal chance of being chosen.
Done by giving each item a unique number, then numbers are generated randomly to choose an item.
Systematic sampling
All items are listed and chosen at regular intervals along the list.
Starting point is random.
Care is take to avoid patterns occurring in data to allow representation.
Cluster sampling
Population has definite groups within it that represent properties of the whole population.
Stratified sampling
When population has definite group with different properties, so a sample is taken from each group.
Each sample is proportional.
Continuous data
Every value with a given range can occur.
Typically measurements of items.
Discrete date
Only certain values can occurs
Counted numbers of items
Representation of categorical data
Bar chart
Pie chart
Representation of discrete data
Bar chart
Pie chart
If grouped in histograms
Representation of continuous data
Histogram
Box plot
What are histograms used for?
Continuous data and grouped discrete data
Frequency density
=frequency/width
Main points to remember about histograms are:
Area represents frequency Bars meet at lower and upper class boundaries
Ways of of measuring histogram data
To the nearest unit
Use of inequalities, e.g. 0≤x<10
Implied bounds, e.g. 0-,10-,15-
Variance of a set of data
Measure of how spread out the data is around the mean
sx = σ^
estimate of the population standard deviation
