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# 2.10 Achievement Objectives

### Excellence

• Conduct an experiment to investigate a situation using statistical methods.
• Conduct an experiment to investigate a situation using statistical methods, with justification.
• Conduct an experiment to investigate a situation using statistical methods, with statistical insight.

This involves showing evidence of using each component of the investigation process.

This involves linking components of the process of investigating a situation by experiment to the context, explaining relevant considerations in the investigation process, and supporting findings with statements which refer to evidence gained from the experiment.

This involves integrating statistical and contextual knowledge throughout the investigation process which may involve reflecting on the process, or considering other relevant variables.

Achievement Standard 2.10 #91265 (link to NZQA)

The process of investigating a situation by experiment involves:

• posing an investigative question about a given experimental situation
• planning the experiment by
• determining appropriate variables and measures
• determining data collection and recording methods
• conducting the experiment and collecting data
• selecting appropriate displays and measures
• discussing displays and measures
• communicating findings in a conclusion.

Note that an experiment requires an intervention and cannot be an observation study.
Experiments can be either,

• Two independent group comparison, or
• Paired comparisons.

### Clarifications

Students need to provide evidence of each component of the investigation process detailed in Explanatory Note 3 of the standard.

Students can be provided with the experimental situation which they will investigate by planning and carrying out an experiment. Planning the experiment is an important part of the evidence for the standard. For higher grades a step up in the quality of the planning is required.

The experimental situation must involve an intervention and be one of two types of design.

### 1. Comparison of two independent groups

The people taking part in the experiment need to be randomly assigned to the two groups (the control group and the treatment group).

A suitable situation could involve investigating the effect of colour on memory. The experiment could involve using a sheet of paper with the 20 objects on it. The intervention in the experiment would be using colour so one group would be shown black and white pictures of the objects and the second group would be shown colour pictures of the objects. The variable that would be investigated would be the number of objects remembered by the different groups.

After carrying out the experiment and collecting and recording their data students need to look at the data from the experiment and discuss what it tells them. Students could produce dot plots and/or box plots of each independent group and discuss things like shape, shift, centre, spread and unusual features

The conclusion should include a ‘suggestive inference’. For example for the colour experiment students might conclude that the use of colour appears to result in the recall of a higher number of objects and for the pulse rate experiment, exercising appears to have caused an increase in the pulse rates.

For Achieved it is sufficient to provide evidence of posing a question to investigate the given experimental situation, planning and carrying out an experiment and recording the results, analysing the data that has been collected and communicating the findings from the analysis.

With justification includes considering related variables and possible effects.

With statistical insight includes considering related variables, possible effects and plans to mitigate against them. It also includes the integration of statistical and contextual information, for example, a student might use contextual knowledge to help explain what is observed, e.g. higher pulse rates after exercise.

### 2. Paired comparison

In a paired comparison ‘before’ and ‘after’ measurements are taken on the same person or object.

A suitable experiment could be investigating the effect of exercise on pulse rates. The intervention would be the exercise. The ‘before’ measurement would be the resting pulse rate and the ‘after’ measurement would be the pulse rate after exercise. The analysis would involve looking at the difference in the pulse rates. An ‘arrow plot’ displaying before and after intervention, dot plots and/or box plots of the differences could be used for the comparison.