1. 14/11/2018
CORRELATION

2. 14/11/2018
Correlation
Correlation tells us about the relationship between two variables
It can be…
positive (going up ↗, so as one increases the other increases)
negative (going down ↘, so as one increases the other decreases)
no correlation (no direction)
It can also be…
strong (points nearly on a straight line)
weak (points have a clear direction but not nearly on a straight line)

3. 14/11/2018
Example
What does this scatter graph show about the relationship between the height and weight of twenty Year 10 boys? 40 45 50 55 60
140
150
160
170
180
190
Height (cm)
Weight (kg)
As height increases, weight increases.
This is called a strong positive correlation.

4. What does this scatter graph show?
14/11/2018
Example
What does this scatter graph show? 50 55 60 65 70 75 80 85 20 40
100
120
Number of cigarettes smoked in a week
Life expectancy
It shows that life expectancy decreases as the number of cigarettes smoked increases.
This is called a weak negative correlation.

5. 14/11/2018 Task Decide whether each of the following graphs shows,
strong positive correlation
strong negative correlation
zero correlation
weak positive correlation
weak negative correlation

6. Petrol consumption (mpg)
14/11/2018
Task – State the type of correlation for each graph.
Extension – Write a sentence to describe the relationship for each one 1
Positive 2
Negative 3
None
Physics test scores
Petrol consumption (mpg)
Height
Maths test scores
Car engine size (cc)
KS 3 Results
There is no relationship between KS 3 results and the height of students.
People with higher maths scores tend to get higher physics scores.
As the engine size of cars increase, they use more petrol. (Less mpg)
People tend to buy more sun cream when the weather is sunnier.
The older the car the less its value.
As the outside air temperature increases, heating bills will be lower. 4
Sales of Sun cream 5 6
Negative
Positive
Negative
Heating bill (£)
Value of car (£)
Outside air temperature
Daily hours of sunshine
Age of car (years)

7. PLOTTING SCATTER GRAPHS
14/11/2018
PLOTTING SCATTER GRAPHS

8. 14/11/2018
Spot the errors! What is wrong with each of these sets of axes?

9. 14/11/2018
Examples – Fill this in on your sheet as we go through it. Then try the second one yourself… 4 5 6 7 8 9 10 11 12 13
Shoe Size 60 65 70 75 80 85 90 95
100
Mass (kg) 74 88 76 78 92 68 97
Mass
Size

10. 14/11/2018
USING SCATTER GRAPHS

11. 14/11/2018
Line of best fit
Is a straight line which is supposed to be a good representation of the pattern / trend of the data
Method
Try to get roughly the same amount of points above the line as below
Experiment by using your ruler as your line, and only draw the line in when you are happy
Your line does NOT have to start at the origin (0, 0)

12. 14/11/2018
Complete the worksheet for plotting scatter graphs and drawing lines of best fit.

13. 14/11/2018 Estimating using the line of best fit
Question 1: If 7 pupils forget to hand in their homework, how many minutes of yoga might Mr Barton do?
Question 2: If Mr Barton does 28 minutes of yoga, how many pupils might have forgotten their homework?
Following the green line up and across gives…
16 minutes
Following the purple line across and down…
14.5 pupils

14. 14/11/2018
Solutions 1)

15. 14/11/2018
Solutions 2)