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MR317 Introduction to Marine Ecology - Biostatistics
LecturesMartin Ryan Seminar RoomMonday 11am, Tuesday 9amTuesday 12 pm, Friday 9 am
MINITAB PracticalsRoom 201 Arts Millenium Building
starting 16/01/06 Monday 2 – 5 pm
Emma HolianRoom 108, Riverside Terrapin
Email: [email protected]
Dr. Jochen EinbeckRoom 209, Áras de Brún
Email: [email protected]
Lecturers:
Lecture Material
• Handouts, notes• Web based material
http://www.nuigalway.ie/maths/je/marine– Notes, these slides– Datasets
Course Content• Basic ideas – revision• Looking at data – summaries, plots, etc• Statistical analyses
– Comparing groups– Regression– Analysis of variance – Simple multivariate methods
• Aspects of study design• Use of MINITAB package
Population : the entire group of objects about which information is required.
Collecting Data
A parameter is a numerical characteristic of the population.
It is a fixed number, but we usually do not know its value.
Unit: any individual member of the population
Sample: a part or subset of the population used to gain information about the population.
Sampling Frame: the list of units from which the sample is chosen.
Geographical/Spatial coordinates.
Variable: a characteristic of a unit to be measured in the sample.
Data are the values that variables can assume.
Variable
Qualitative Quantitative
Discrete Continuous
Nominal Ordinal
The value of the statistic changes from sample to
sample.
Statistics ARE numbers derived from a sample
of data.
Example 1
Population: Irish Sea
Unit ?
Sample ?
Variable ?
Sampling Frame ?
PopulationParameters
Inference
SampleStatistics
Sample
Inference is the process of making decisions about a
population based on information contained in a
sample from that population.
• Descriptive statisticsconsists of the collection, organisation, summarisation, and presentation of data.
• Inferential statisticsconsists of generalisingfrom samples to populations, performing hypothesis testing, determining relationships among variables, and making predictions.
General philosophy
How do we select a small subset of a population
representative of the whole population?
Using your best judgement, take a representative sample
of 6 circles from the population of 60 circles and use the sample mean as an
estimate of the true population mean
1
1.5
2 3
2.5
0.5N=60
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
0
50
100
150
200
250
Judgement
Freq
uenc
yJudgement Sample
0.5 1.0 1.5
0
50
100
150
SRS
Freq
uenc
ySimple Random Sample
0.5 1.5 2.5
0
50
100
150
Judgement and SRS
Freq
uenc
y
One consequence of natural variation is that two samples drawn by the same method from the same
population will give somewhat different estimates of the population parameters (sampling variation).
Understanding variation
Statistics deals with discriminating between variation that is scientifically interesting and
variation that just reflects background variation.