Assignment 1 – Experimental Research Design Case Study
Task Outline
Task Guidelines
Weighting/Marks: 20% / 20 marks
Assessment Type: Written Case Study Evaluation
Submission Type: Word document using provided template on StudyDesk Submission Process: via TurnItIn link on StudyDesk
Word Limit: Part A – 1.5 pages; Part B – 0.5 pages per threat to validity addressed. Font Style: As per the provided template.
References: No referencing required.
Task / Purpose
Research design will include threats to interval validity that are present and that have not been addressed by the structure of the current research design.
In Part A of the assignment, students will need to go through the list of possible threats to internal validity (as covered in the course) and assess if each threat to validity is present or not. For threats to internal validity that are not present, provide an explanation about why this threat is not present.
For example, has the research design incorporated a particular feature that has reduced this threat? For threats to internal validity that are present, provide an explanation about how this has come about. That is, what has the researcher done (or not done) to have this threat to internal validity present in the current design.
In Part B of the assignment, students will then focus on addressing the threats to internal validity that are still present as identified in Part A. Firstly, students should propose a change to the current experimental design that addresses one of these threats to internal validity. Secondly, the student should then explain (i.e., justify) how the specific change in the experimental design addresses the threat to internal validity.
Please note that a single change to the experimental design may address more than one threat to internal validity. However, please ensure your responses to Part B are broken up per threat being addressed. That is, don’t attempt to merge together two or three threats into one.
Please also note that the changes you make to the experimental design should be specific to a threat to internal validity identified as being present in Part A. Threats to internal validity that are not present as assessed in Part A should not be included in Part B. Furthermore, changes to the experimental design for other reasons (e.g. improving statistical power, using a gold standard measuring technique) are not relevant here. Again, proposed changes to the experimental design

should only be applied to address the threats to internal validity that are present as identified in Part A.
(In part B, for each threat to internal validity that is still present,
you need to have 3 sections:
1. Threat to Internal Validity Being Addressed (name of the threat).
2. Proposed modification that addresses the threat.
3. Explanation of how this proposed change addresses this threat.
So, the template subheading will be useful in organising your answers.)
Use the template on StudyDesk to provide your evaluation and propose changes to the experimental design.

Case Study
A researcher is wanting to know the effect of playing soccer on bone density composition in the hips and legs of children. They recruit all the players from one Under 12’s girls’ team that represents one suburb in a city-wide league. They also recruit subjects to form a control group, where they currently do not participate in any sport or physical activity. The subjects in the soccer playing group participate in one full season, consisting of training twice a week and playing one game per week for 20 weeks. Before and after the season, the subjects in both the soccer playing and control groups have their bone mineral density tested using a calibrated DEXA machine. The research assistant, who is a trained DEXA operator and unaware of which group each subject is in, performs the bone mineral density testing. A coach, not part of the research team, runs the training and games throughout the season. The coach ensures the players train in a way that allows them to complete the season. All participants, across the experimental and control groups, completed all of the training / games and testing sessions.

Marking Criteria
Explanation
For the threats to internal validity that have been addressed by the current experimental design, provide a clear and concise explanation detailing how this was achieved. That is, what research design feature was implemented or explain how the particular threat to internal validity is not present because of the context of the experiment.
For the threats to internal validity that are not addressed, identify these and explain why each threat to internal validity can affect this specific experiment (8 marks).
Modification
Provide and describe a modification to the experimental design for each threat to internal validity that was not addressed by the original experimental design (3 marks).
Justification
Provide a clear and concise explanation of how each modification provided addresses the threat to internal validity nominated (6 marks).
Communication
Consistent use of good grammar and punctuation, and the use of the template without modifications (3 marks).
Total: 20 marks