# Mathematics and Statistics - annotated exemplar Level 3 AS91583

## Conduct an experiment to investigate a situation using experimental design principles (3.11)

 Read the STANDARD TKI Mathematics and Statistics Assessment Resources Download all these exemplars and commentary (PDF, 546KB)

This annotated exemplar is intended for teacher use only. The student work shown does not always represent a complete sample of what is required. Selected extracts are used, focused on the grade boundaries, in order to assist assessors to make judgements at the national standard.

Last updated June 2019.

There is new student evidence for High Merit and High Not Achieved.

All annotations have been altered to better illustrate the requirements of the standard. The assessment resource that was used to collect the student evidence has been amended.

### Low Excellence

Commentary
Student work extract

Student 1 (PDF, 130KB)

For Excellence, the student needs to conduct an experiment to investigate a situation using experimental design principles, with statistical insight.

This involves integrating statistical and contextual knowledge throughout the investigation process, and may include reflecting about the process, discussing how possible sources of variation were dealt with during the design phase; considering other relevant variables.

This evidence is from a student’s response to the TKI task ‘Tricky questions’.

The student has integrated contextual knowledge gained from research when posing an investigative question about a given experimental situation (1) and when designing the experiment (2).

The student has also discussed how possible sources of variation were dealt with during the design phase (3) and made an appropriate formal statistical inference by assessing and interpreting the strength of evidence about the causal relationship (4).

When communicating their findings, the student has considered other relevant variables that may contribute to variation (5) and in their conclusion, they have reflected on the process by discussing the possible implications of increasing the value of the anchor (6).

This extract is from a student response which also included evidence of selecting and using appropriate displays and summary statistics to an appropriate level for the award of Excellence.

For a more secure Excellence, the student could have reflected on the process more fully by discussing the effect of the value of the anchor relative to the true population of Venezuela. The student could also have explained how the results of the experiment were consistent with the research studies discussed when posing their question.

### High Merit

Commentary
Student work extract

Student 2 (PDF, 178KB)

For Merit, the student needs to conduct an experiment to investigate a situation using experimental design principles, with justification.

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 evidence is from a student’s response to the TKI task ‘Estimation’.

The student has linked the development of a suitable investigative question about a given experimental situation (1) and the design of the experiment (2) to the context. They have explained relevant considerations in the design phase (3) and when managing possible sources of variation (4).

The student has also made an appropriate formal statistical inference which has been justified (5) and in their conclusion, there is evidence of linking findings to the context (6).

This extract is from a student response which also included evidence of selecting and discussing appropriate displays and summary statistics to an appropriate level for the award of Merit.

To reach Excellence, the student would need to integrate the information found in their research into the context in both their introduction and conclusion. The student could also consider in more depth other relevant variables that may have contributed to the variation.

### Low Merit

Commentary
Student work extract

Student 3 (PDF, 116KB)

For Merit, the student needs to conduct an experiment to investigate a situation using experimental design principles, with justification.

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 evidence is from a student’s response to the TKI task ‘Tricky questions’.

The student has linked the development of a suitable investigative question about a given experimental situation (1) and the design of the experiment (2) to the context. They have explained relevant considerations in the design phase (3) and when managing possible sources of variation (4).

In their conclusion the student has made an appropriate formal statistical inference with their findings being supported with evidence gained from the experiment (5).

This extract is from a student response which also included evidence of selecting and using appropriate displays and summary statistics to an appropriate level for the award of Merit.

For a more secure Merit, the student could strengthen the justification of decisions made in planning the experiment. For example, by providing a more detailed description of how they managed sources of variation and identifying the variables that cannot be controlled.

The student could also provide stronger evidence of linking the research to the situation being investigated and to the findings.

### High Achieved

Commentary
Student work extract

Student 4 (PDF, 139KB)

For Achieved, the student needs to conduct an experiment to investigate a situation using experimental design principles.

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

This evidence is from a student’s response to the TKI task ‘Tricky questions’.

The student has posed an investigative question about a given experimental situation and provided some evidence of researching the context (1).

Experimental design principles are shown by the student selecting the experimental units (2), determining treatment and response variables (3), determining the allocation of treatments to experimental units (4), determining data collection and recording methods (5) and discussing how they considered other possible sources of variation (6).

In their conclusion the student has made an appropriate formal statistical inference with their findings being supported with evidence gained from the experiment (7).

This extract is from a student response which also included evidence of conducting the experiment and selecting and using appropriate displays and summary statistics to an appropriate level for Achieved.

To reach Merit, the student could link their prediction of what they think will happen in their experiment to the context. The student should also describe in more detail the experimental plan, particularly the treatment variable and the method of random allocation and link the design of the plan and their findings more closely to the context.

When making their inference, the student should also interpret the strength of evidence more clearly, and indicate who the results apply to.

### Low Achieved

Commentary
Student work extract

Student 5 (PDF, 135KB)

For Achieved, the student needs to conduct an experiment to investigate a situation using experimental design principles.

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

This evidence is from a student’s response to the TKI task ‘Tricky questions’.

The student has posed an investigative question about a given experimental situation (1), planned the experiment using experimental design principles by selecting experimental units (2), determining treatment and response variables (3), determining the allocation of treatments to experimental units (4), determining data collection and recording methods (5) and considering other sources of variation (6).

The student has also made an appropriate formal statistical inference and communicated findings in a conclusion (7).

This extract is from a student response which also included evidence of conducting the experiment, selecting and using appropriate displays and summary statistics to an appropriate level for the award of Achieved.

For a more secure Achieved, the student, when posing a suitable investigative question about a given experimental situation, needs to provide some evidence of researching the context.

In their experimental plan, the student could provide more detailed discussion, such as explaining how the surveys were distributed. The answer to the question should also be described more clearly.

### High Not Achieved

Commentary
Student work extract

Student 6 (PDF, 213KB)

For Achieved, the student needs to conduct an experiment to investigate a situation using experimental design principles.

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

This evidence is from a student’s response to the TKI task ‘Estimation’.

The student has posed an investigative question about a given experimental situation (1), planned the experiment using experimental design principles by selecting experimental units (2), determining treatment and response variables (3), determining the allocation of treatments to experimental units (4), determining data collection and recording methods (5), considering sources of variation (6) and selecting and using appropriate displays and summary statistics (7).

To reach Achieved, the student needs to make a correct inference. The student should also strengthen the plan by explaining more clearly how the experiment was conducted.

When posing the investigative question about a given experimental situation, the student needs to provide some evidence of researching the context.