Dr Richy Hetherington and Dr Kim Pearce Todays Session Start a live experiment The scientific method in context You are the information generation Planning experiments Replication ID: 498253
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Slide1
Experimental Design and Efficient Research
Dr. Richy Hetherington
and Dr.
Kim PearceSlide2
Today’s Session
Start a live experiment
The scientific method
in
context
You are the
information generation
Planning
experiments
Replication
,
randomisation
and
controls
When sample size has to be small
Simple tips for analysis
The best help for youSlide3
An Experiment
I’m going to hand some cards out
take a one
Yellow for boys
Purple for girls
Write your 2D finger length4D finger length
Hand in the cards & we’ll
Come back to this laterSlide4
The Scientific Method in Context
1.Observe an interesting or puzzling phenomenon
2. Make a hypothesis to explain the phenomenon
3. Devise a test to see if your hypothesis is true
4. Carry out your test
5. analyse your results6. State whether your hypothesis is correct if not at least have some information to help come up with a new hypothesis.Slide5
Take Home Messages no. 1 and 2
Leave no stone unturned
(use all possible sources of information)
Training to help (workshops throughout the year):
Introduction to Library Facilities,
Building robust search strategies - how to cover all the bases
Evaluating electronic information - Sorting the wheat from the chaff Information Databases
Advanced Medline
Integrated Library and IT Skills Assimilation
SDIs
and Alerting Services
Think about what is coming nextSlide6
For Example: This workshopSlide7
Planning Your Experiments
Take home message 3.
Don’t believe everything you read
See
: Can I believe it (3rd Feb)
& Introduction to Critical Appraisal (online)Use non-rigorous experiments but be prepared to repeat them with rigour
Take home message 4.
Get as much help as is available in setting up your experiments
(shy
bairns
get
nowt
!)Slide8
Make every result count
Take home message 5.
Set up your experiments so all eventualities are interesting
Results can be meaningful and interesting without being statistically significant
Also reporting non-significant findings avoids others from needlessly repeating that experimentSlide9
Get a statisticians help now
“To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of.”
Dr. R. A. Fisher ca1938Slide10
Subject Selection and Randomisation
Make sure the sample you take is representative of what you are testing
Samples should be made randomly to avoid bias
Double Blind Randomising means the researcher does not know which sample is being treated and which is the controlSlide11
Replication
Data from separate experiment should not be combined
Datasets can be treated as replicates if all other variables are the same or weighted
Analysis of replicates indicate the amount of variation in a resultSlide12
Controls
Control for everything you can
Take as much care with controls as with samples
Each experiment requires its own controlSlide13
Where sample sizes need to be small
Non-Human
Primates often n=1
Animal
experimentationSlide14
Analysis Software
There are many statistics packages available.
MINITAB & SPSS are the most widely used & among the most straightforward to learn.
The ISS (computing service) provides support to users.
Other packages may be used in various schools.
Excel is not recommended as a piece of analysis software.Slide15
The Experiment
Why 2D to 4D finger length ratio?
Many interesting characteristics attributed
Low ratios
in men: sporty, musical, aggressive
in women: more fertileHigh ratiosIn men: better exam resultsIn women: fertilitySlide16
But are the gender differences real?
Differences in the 2nd to 4th digit length ratio in humans reflect shifts along the common
allometric
line.
Kratochvíl
L
, Flegr J.Biology Letters 2009Slide17
Summary
First step is always plots & descriptive statistics
Test should be kept as straightforward as possible as this makes interpretation/presentation of results easier.
There is no reason to attempt complicated techniques when a simple test would work just as wellSlide18
So what is right for you
If you weren’t sure about anything mentioned here or you need refresher in stats –
ISRU very basic stats (45 minutes)
ISRU basic stats (3 hours) clinical / pure science
Overview of Stats packages
SPSS for beginners
Advanced SPSSIn your 2nd year and you need a more thorough knowledge of medical stats- The medical stats course or the Statistical Methods course (Mres)
One to one stats is useful for anyone at the right time
Maths aid available daily in term time