Correlation part 1
Relationship between variables...
We are covering...
● Idea of correlation
● Plotting scatter diagrams
● Describing the pattern of points
● Drawing line of best fit and using the LOBF to
● Finding the difference between interpolation
Activity 1: Read the following
● Look for holes in the arguments
● Can you state what the fallacies might be?
● Are they valid and false?
● Or just invalid?
“Children brought up in homes with
more household appliances tend to
perform better in school. Therefore,
household appliances improve
“Teens involved in violent crimes tend
to play violent video games. Therefore,
playing violent video games causes
teenagers to get involved in criminal
Serge Rachmaninov could play a left hand chord of C E-Flat G C G
Activity 2: plot scatter diagram
● Plot your own scatter diagram of the hand span
and forearm data
● What scale are you going to use?
● Where will you start and finish the axes?
● Compare your scatter diagram with someone
else. Does the pattern of crosses look about the
Strong No Moderate
Positive correlation, Negative
Correlation little Correlation
● Plot a scatter diagram of Handspan vs Shoe
Size from this data set
● Describe the pattern using the vocabulary
developed on the last slide
● Do you think that the relationship between shoe
size and hand span might be stronger than the
relationship between hand span and fore arm
length? What basis have you for your opinion?
Line of best fit
Only for medium to strong correlations...
value of the Y
variable from the
Activity 3: Draw LOBF
● Take your plot of the forearm and handspan length and
draw a line of best fit on the graph
● Compare your LOBF with someone else. Is yours
shallow or steep or somewhere in the middle?
● Use your graph to predict the forearm length of
someone with a hand span of 20.5 cm
● Use your graph to predict the hand span of someone
whose forearm is 48cm long
● How do the results compare with others? Which
prediction varies more?
Interpolation and extrapolation
Safe data processing
Y The LOBF has
beyond the range
of the data
outside the range
of the data points
● Draw a LOBF on your shoe size and hand span
● Use your LOBF to predict the hand span of
someone with a shoe size of 7½
● Use the LOBF to predict the shoe size of
someone with a hand span of 24.5 cm
● Which prediction is the most reliable. Write a
sentence to two explaining your answer