MR317 Introduction to Marine
Ecology - Biostatistics
Lectures
Martin Ryan Seminar Room
Monday 11am, Tuesday 9am
Tuesday 12 pm, Friday 9 am
MINITAB Practicals
Room 201 Arts Millenium Building
starting 16/01/06
Monday 2 – 5 pm
Lecturers:
Emma Holian
Room 108, Riverside Terrapin
Email: emma.holian@nuigalway.ie
Dr. Jochen Einbeck
Room 209, Áras de Brún
Email: jochen.einbeck@nuigalway.ie
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
–
–
–
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Comparing groups
Regression
Analysis of variance
Simple multivariate methods
• Aspects of study design
• Use of MINITAB package
Collecting Data
Population : the entire
group of objects about
which information is
required.
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
Nominal Ordinal
Discrete
Continuous
Statistics ARE numbers
derived from a sample
of data.
The value of the statistic
changes from sample to
sample.
Example 1
Population: Irish Sea
Unit ?
Sample ?
Variable ?
Sampling Frame ?
Population
Parameters
Inference
Sample
Sample
Statistics
Inference is the process of
making decisions about a
population based on
information contained in a
sample from that population.
General philosophy
• Descriptive statistics
consists of the
collection,
organisation,
summarisation, and
presentation of data.
• Inferential statistics
consists of generalising
from samples to
populations, performing
hypothesis testing,
determining relationships
among variables, and
making predictions.
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
N=60
0.5
1
2.5
1.5
2
3
Judgement Sample
250
Frequency
200
150
100
50
0
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Judgement
2.0
2.2
2.4
2.6
Simple Random Sample
Frequency
150
100
50
0
0.5
1.0
SRS
1.5
Frequency
150
100
50
0
0.5
1.5
Judgement and SRS
2.5
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.