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Catch the correlation

By David, 10 March 2015 Activity

Can you spot the links between the graphs, and catch the correlations?

You will need

You will need these items.

• Scissors
• Copy of the graphs sheet, printed on transparent sheet.
• Sheet of white paper
• Pen and notebook

What to do

1. Cut out each graph from the sheet.

Try to match the curves as closely as possible.

2. Choose two graphs, and lay one on top of the other, with a plain white sheet of paper behind. Make sure the months line up. Do the curves on the graph match?
3. Move the two graphs so the curves match the best you can make them. Do the months line up now?
4. Choose two different graphs and repeat the matching process. Try several different pairs.

How can you make these two graphs match?

5. Can you describe the relationships between each of the graphs? Can you think of a good reason why they don’t match perfectly?

What’s happening?

None of these graphs line up perfectly, but they are all linked. What we have found is a correlation. The graphs in this activity are all seasonal, rising and falling in a yearly cycle.

We can work out some of the reasons the graphs don’t line up perfectly. Temperature lags a bit behind day length, which means the hottest days are a bit after the longest days. This is because it takes a while for sunlight to heat the Earth. Several long days in a row will make the ground get hotter and hotter.

London’s weather is similar to Canberra, but the seasons are flipped. This is because they are in different hemispheres on Earth. When the days are long in the southern hemisphere, they are short in the northern hemisphere.