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Back to CensusAtSchool home page CaSQ 17B - Scatter plots: Correlation and fitting a trend line

You can download this activity as a rich text file (RTF) using the link at the bottom of the page.

How to: Get a Random Sample from CensusAtSchool

Go to the CensusAtSchool Random Sampler to download a sample.

Reference year: (select year) Sample size: At least 30 students

Select questions: Year level, Concentration Game

Location:
Select Location Year level: All

To project privacy there is a rule built into the sampler that the requested sample size cannot exceed 10% of the respondents for the parameters entered.


This task is designed to be completed by hand drawing a scatterplot. It can also be completed using Excel or a CAS calculator.

Task:

1. Using your CensusAtSchool random sample, enter both sets of thirty numbers as:
      • a table in your workbook, or
      • two columns in Excel, or
      • two separate lists in your CAS calculator.


2. Create a scatter plot with your data.
      • Think about which set of data is the independent and dependent variable
      • Plan your axes to include the highest and lowest values in the data
      • Include a title that includes the variable names.


3. Look at your graph. Can you see any trend or pattern to the data? Complete this sentence:

As school year level __________________, concentration time __________________.


4. Examine your scatter plot and circle the appropriate description:
    Direction
    Form
    Strength
    Positive Negative
    Linear Non-linear
    Strong Moderate Weak

5. Fit a trend line (sometimes called the line of best fit) to the data and complete the following sentence:
Each time the year level increases by 1 (year), the concentration time _________________ by ____ (seconds).


    6. Estimate the value of the correlation coefficient (r) and explain what this indicates about the strength of the relationship.



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    Extension:

    7. Use the Random Sampler to choose your own data to create a scatterplot.

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    8. Use linear regression to calculate the trend line and the correlation coefficient.

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    9. Explain what this correlation coefficient indicates about the strength of the relationship.

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    Download the full activity:


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