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 CaSQ 17B - Scatter plots: Correlation and fitting a trend line
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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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To provide any feedback regarding this activity, please contact ABS Education Services on 1800 623 273 or email education@abs.gov.au.
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This page last updated 12 February 2013 | 
