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Statistics and modelling 3.5 Select and analyse continuous bi-variate data

Achievement criteria

The level of achievement that you reach is decided by the questions that you answer correctly.

Achievement

• You select and analyse continuous bi-variate data.
• You may collect the data or it may be provided. It should be data for which a linear model is appropriate. Where the data is provided it will involve more than one pair of variables from which you select a pair.
• The analysis will involve:
  • developing a purpose statement from the data selected
  • graphing data
  • using regression to establish a linear relationship between a pair of variables
  • describing the relationship between at least one pair of variables in context.

Achievement with Merit

• You need to reach Achievement.
• You carry out an in-depth analysis of bi-variate data.
• Your analysis will include some of the following:
  • comparing the relationship between more than one pair of variables
  • discussing the appropriateness of the model
  • interpreting correlation coefficients, r, and coefficients of determination, R², when appropriate
  • making predictions from regression equations (interpolation and/or extrapolation)
  • use of residuals
  • discussing the difference between correlation and causality when appropriate.

Achievement with Excellence

• You need to reach Achievement with Merit.
• You report on the validity of the analysis.
• The report will include justified comments on some of the following:
  • method(s) of analysis
  • assumptions made
  • limitations
  • improving regression models, for example discussing the effect of outliers, fitting piecewise or non-linear models
  • alternative approaches
  • data source or data collection method if you collect your own data
  • potential sources of bias
  • relevance and usefulness of evidence
  • how widely the findings can be applied.

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