Statistics
What is statistics?
There are three parts to statistics:
Gathering data
This where you might make a survey, count cars, take tests etc.
Summarising data
This means putting the information together usually by making a graph. This makes it easier to see and emphasise the most important aspects of the data.
Analysing data (or inferring from data = inferential statistics)
This is where we use the data to make statements or help to prove an inference.
Analysing Data
Analysing data is possibly the most important part of statistics because it:
-gives us information
-helps us to prove ideas or reasons
-shows us needs or things to change
Statements
Bananas are the most popular fruit because graph is highest for bananas.
Pears are the least popular fruit.
Apples are the second most popular.
34 people voted.
Analysing Data
When we analyse data we need to be careful to read it correctly.
Statements should be made facts.
Our facts need to be true.
Summarising Data
We summarise the data that we collect by making graphs.
We make graphs to ‘make sense’ out of our data.
Different graphs have different purposes.
We need to choose the graph that makes the most sense for our data.
Graphs need labels. Without labels it is hard to make sense from the data.
Bar Graph
A bar graph is used for comparing amounts ( how much).
The groups of data ( different coloured bars) are different but part of a similar ‘family’. ( types of fruit)
We use a bar graph to notice the gaps between groups.
Notice the labels. How do they help make sense of the data?
Line Graph
A line graph shows change in a sequence.
We call this a continuum.
This is a very good graph to show how data changes over time.
Notice the continuum. Rather than groups we can see a sequence of numbers. 1,2,3...
Stem and Leaf Graph
A stem and leaf graph also uses a sequence. A continuum.
Stem and leaf graphs are used for quickly organising lots of data with lots of numbers.
Notice the continuum. Rather than groups we can see a sequence of numbers. 1,2,3...
Here is a lot of data.
Can you spot the stem?
Can you see the leaves?
Notice the labels.
Stem and leaf graphs can also look like this.
Pie Graph
A pie graph shows the parts of a whole.
Eg. a whole class
The groups of data ( different coloured pieces) are different but part of a similar ‘family’. (movies)
We use a bar graph to notice the percentage or fraction a group represents.
Labels are so important!
Summarising Data
Gathering Data
Before we can summarise our data and analyse the graphs we need to get the data.
We get data by investigating.
This means observing, asking and counting.
My Statistical Investigation
Step 1:
Ask the big question.
This is a question that is important to you and has up to 5 clear multi-choice answers.
Question: How many families use plastic bags when shopping?
Choice 1: Use plastic bags
Choice 2: Use boxes instead of plastic bags
Choice 3: Bring my own reusable bags from home
Choice 4: Use plastic bags sometimes and other bags or boxes from home.
Questions
Transport
School
Fun
Sport
What type of animal or insect do you prefer?
What unusual animal would you prefer as a pet?
What’s your favourite video game?
My Statistical Investigation
Step 2:
Carefully and accurately collect your information.
You will need to make sure that:
Use plastic bags | |
Use boxes instead of plastic bags | |
Own reusable bags from home | |
Use plastic bags sometimes and other bags or boxes from home | |
My Statistical Investigation
Step 3:
Summarise your information in a graph.
Step 4:
Make analytical statements about your graph.