1. ANW2036 Industrial Project
Principles of Experimental Design

2. For your consideration….
The story so far…..
Planning your project.
Referencing workshops & searching for information
Risk and ethics…..do we need to review this?
Qualitative Research Techniques.
TODAY: Experimental Design (Quantitative)
The Scientific Method

3. The research cycle

4. Why experiment?
To determine the cause(s) of variation in the response.
To find conditions under which the optimal response is achieved.
To compare responses at different levels of controllable variables.
To develop a model for predicting responses.

5. The building blocks
Treatments – different combinations of conditions that are to be tested. Treatments set at levels.
Experimental unit – subject on which a treatment will be applied and from which a response will be elicited.
Responses – outcomes that will be elicited from experimental units after treatments have been applied.
Q. Milk powder trial on lamb growth sponsored by VOLAC. What are the treatments, experimental units and responses?

6. Building blocks (cont.)
Experimental design - planning the efficient and systematic collection of responses from experimental units.
Replication – observing individual responses of multiple experimental units under identical experimental conditions.
Repeated measurements
Blocking – partition the experimental units into groups that are homogeneous in some sense.
Randomisation – non-systematic assignment of experimental units to treatments. Why?

7. Methods of data collection
Observation
i. Select a proportion of the population (=sample).
ii. Measure or observe the values of the variables in question for the selected elements.
Experimentation
i. Manipulate the values (or levels) of one or more (independent) variables or treatments.
ii. Observe the corresponding change in the values of one or more (dependent) variables or responses.

8. Example 1
TITLE: A preliminary study of behavioural and auditory recordings of rabbits before and during fireworks.
AIM:
To quantify any changes in the behaviour of domestic rabbits exposed to the sounds of fireworks.
Objective 1: Record rabbit behaviour before and during bonfire season.
Objective 2: Record sound levels at site of behaviour observations.
Objective 3: Compare the behaviour of rabbits before and during the bonfire season.
Objective 4: Compare the behaviour of rabbits during baseline (no firework) and peak (firework) sound levels.
Q. How would you do it?

9. Example 2

10. Q. How would you do it?

16. Example 3

17. Example 3 Q. How would you do it?
TITLE: Ecological sensitivity of subarctic mountain vegetation to anthropogenic disturbance in the Icelandic highlands.
AIMS:
To evaluate the impact of experimental trampling on subarctic native mountain vegetation using methods stipulated by Cole (1993).
To monitor the efficacy of native turf transplants for re- vegetating hiker trails in subarctic mountain environs.
To define the tolerance of native Icelandic flora to simulated trampling.
REFERENCE:
Cole, D.N. (1993) Experimental trampling of vegetation: standard experimental procedures. Biological Conservation 63,
Q. How would you do it?

18. Effective experimental design considers…..
Systematic error that leads to bias when estimating differences in responses between treatments.
Precision.
Estimates error (Q. How?).
Validity – that the experimental units are a sample of the population in question.

19. Designing valid experiments
Define (precise) objectives.
Identify all potential sources of variation and limit them.
Conduct a pilot study and specify the ‘hypothesized model’.
Outline the analyses to be conducted and design your experiment with subsequent statistical analyses in mind.
Estimate the required sample size using results from the pilot study, or revise qualitative (i.e.: observational) methods.
Review your decision making and begin the experiment.

20. Equine Therapy
Scenario: The Equine Therapy Centre has for years treated performance horses for an array of ailments, yet to date the evidence base of suggested hydrotherapy techniques is limited. The Centre Manager is keen to gauge the efficacy of cold spa treatments on tendon and ligament injury rehabilitation for horses treated at the Centre. Design a study to tackle: ‘Response of equine lower leg injuries to cold spa bath hydrotherapy’

21. Animal Studies / conservation
Scenario: Detection dogs are increasingly part of a global effort to tackle wildlife crime. From intercepting illegal wildlife to finding illegal wildlife products smuggled through airports, shipping ports and public transportation centres – the humble pooch has never been in such demand! Yet now they are also being used in conservation work - detection dogs could help to detect elusive animals. With our harvest mouse project in mind, design an experiment to ‘evaluate the efficacy of a wildlife detection dog versus more traditional survey methods’.

22. Agriculture
Scenario: For many years agronomists have used a simple ‘W’ sampling method for gathering parameters in the field including crop and soil measurements. Yet is this sampling method sufficiently robust, and does it provide the same insight as the more intensive grid sampling technique? Using winter wheat crops growing on medium soils in the East Midlands, can you provide an answer?

23. Task in small groups: Pick one and produce a working title.
Suggest a structure for the investigation, naming the various sections.
State a series of aims / objectives / hypotheses.
Devise an experimental methodology – consider sampling effort and standardised methods (review peer reviewed materials online to inform on this).
Suggest statistical comparisons to test your hypothesis.
Share your findings – critical comments?

24. Designing valid experiments
Finally, for your current idea consider the following :
Define a (more precise) hypothesis for your ‘experiment’. This you may have already done, but there may have been changes.
Outline the likely analyses to be conducted and consider your approach with subsequent statistical analyses in mind. Do you need a ‘control’?
Identify potential sources of variation and bias and try to reduce them.
Estimate the required sample size - how many is ‘enough’? What is your experimental design?
Present and defend your approach to a fellow peer.

25. Summary
The process of data acquisition is called sampling and a large number of observations are preferred.
Methods of sampling vary (random vs. regular), but in all cases the sets of observations are called variables.
An experiment occurs when anything is altered or controlled by the investigator. The condition being controlled is called a factor, and different levels used are called treatments.
Consider having a control for comparative purposes.
Experimental design is influenced by the hypothesis being tested.

26. Designing your industrial project : conclusive remarks
Q. Can you now use these techniques for your actual project?

27. Sources for further information
Ready to Research portal: Dytham, C. (2011) Choosing and Using Statistics, 3rd Edition. Wiley-Blackwell. Gordon, M.S. & Bartol, S.M. (eds) (2004) Experimental Approaches to Conservation Biology. Berkeley: University of California Press. Ruxton, G.D. & Colegrave, N. (2011) Experimental Design for the Life Sciences. OUP.

28. Task (homework)
Next time you read a scientific paper pay particular heed to the methods section and experimental design. Evaluate the experimental design by considering the following:
i. Is the experimental design and subsequent method valid? Could the aim / hypotheses of the study by achieved in an alternative way? How could you improve it?
ii. Is there bias in your paper caused by the experimental design? If so, how could the experimental method / design be revised to eliminate this?

29. Next Session – you tell me!
Would you like to carry out a mini- ‘experiment’?!
All requests for equipment should be ed to