Avenir,Chamique

Pacheco Gimuel

Alfred Serato

A subset of a population on which the information is obtained

Goal: Get an accurate picture of the population from the sample

RANDOM SAMPLING

Equal chance of being selected

Choose me!

Choose me!Choose me!

Choose me!

Choose me!

Choose me! Choose me!

SIMPLE RANDOM SAMPLING

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Tools:1. Fishbowl/ Lots (with replacement)2. Random Number Table3. Random number generator in the

calculator or computer

Random Assignment – every participant in the experiment has an equal chance of being assigned to any of the experimental or control conditions being compared.

Random Selection – every member of population has an equal chance of being selected to be a member of the sample.

Systematic sampling

Systematic sampling

Convenience sampling

Purposive Sampling

The selection of a sample is based on

previous knowledge of a population specific purpose of the research

Purposive Sampling

different from convenience sampling

researchers do not simply study whoever is available

but use their judgement to select a sample which they believe will provide the data they need

Coning and Quartering

Quadrat sampling

Transect Lines

Water Sampling

Coning and Quartering

For granular or powdered samples

Procedure

• Form a conical heap• Spread it out into a circular flat cake• Divide the cake radially into

quarters• Choose two opposite quarters;

combine• Discard the other two quarters• Repeat as many times as needed to

get desired amount

Coning and Quartering • Form a conical heap

Coning and Quartering •Spread it out into a circular flat cake

Coning and Quartering • Divide the cake radially into quarters

Coning and Quartering •Choose two opposite quarters; combine

Coning and Quartering •Discard the other two quarters

•Repeat as many times as needed to get desired amount

Quadrat sampling

-A small area of ground marked out as sampleof a larger area

Purpose: to make a detailed description and record numerical data

For sampling objects that do not move –vegetation or more or less sedentary animals

Quadrat sampling

Quadrat sampling

A frame of predetermined area –placed on the ground

Data: number of individuals per unit area

Decisions:- quadrat size (usually 1m x 1m)- quadrat shape (usually square)- where to put it- how many quadrats- what rules to set

Quadrat sampling

Quadrat sampling

Quadrat sampling

Random- Throwing quadrat

Quadrat sampling

Quadrat sampling

Quadrat sampling

Systematic- using grids

- divide the area into squares of equal sizes

- locate the quadrats by picking coordinates randomly

Quadrat sampling

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Quadrat sampling

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Transect Lines

- A line (usually straight) laid out on a sampling site-Observations are made in a systematic wayalong the line

Decision:- where to mark out the transect- how long- how many- how far apart- intervals between obseervations

Transect Lines

Transect LinesLine Transect- individuals touching the tape

are recorded

-two parallel lines are marked out,individuals between these lines are recorded.

-similar to the line transect

-abundance, presence or absence of species

Transect : Ladder Transect

Considerations1)Type of water body.

2Tests to be performed on the sample.

3)Volume of the sample

4)Container to use

5)Cleaning procedure for container.

6)Water collection technique

7)Transporting and storage

8)How soon to process the sample

- Collect a sample by the hand-dip method if the stream is well mixed.

-Open a sterile bottle ;grasp the bottle near the base , with hand and arm on downstream side of the bottle.

-Without rinsing , plunge the bottle opening downward below the water surface. Allow the bottle to fill with the opening point slightly upward into the current.

-Remove the bottle with the opening pointed upward toward the water and tightly cap it, allowing about 2.5 to 5 cm of headspace.

-This procedure minimizes the collection of the surface film and avoids contact with the streambed.

1)Clean bottles and cap with dilate non phosphate, laboratory-grade

detergent, rinse it 3 times with hot tap and 3 times with deionized or distilled water and sterilize it by

autoclaving.

2)Collect approximately 800mL of stream water.

3)Leave at least an inch of headspace in the bottle to allow adequate mixing and aeration.

4)For E.Coli: Process the samples within 6

hours.

Store sample on ice in cooler or

refrigerator before processing.

Aczel, Amir D. 1995, Statistics and Concepts and Applications, Chicago , Richard D . Irvin Inc.

Beach,David P. and Alvager, Torsten K.E,1992. Handbook for Scientific and Technical Research, New Jersey, Prentice Hall.

Brace, Charles H. and Brase, Corrine P. 1995. Understandable Statistics. Fifth Edition . Lexington, Massachussetts D.C Health and Company.

David, Fely P.,2002. Understanding and doing Research: A handbook for Beginners.TrialEdition. Iloilo City.

Kumar, Ranjit, 1996, Research Methodology. Australia Addison Wesley Longman. Rivera, Maximiano M. Jr. and Rivera, Roela Victoria,1996. Practical Guide to Thesis and Dissertation Writing. Manila, Philippines.

Sevilla Consuelo,G.et.al 1998. Research Methods, Revised Edition, Manila Rex bookstore.Field Sampling. Us geological Survey Ohio District Microbiology Laboratory. 2003. Online. Internet: http://oh.water.usgs.gov/micro/fldsmpl.html/(20 Oct 2006)

Why it is advantageous to study a sample.

Generating random numbers.

Random Selection is employed when every member of a population has an equal chance of being selected to be a member of the sample.

Cluster Sampling is a non-random sampling technique.

Used for granular or powdery samples.

To mark out a small area as a sample out of a large area.

Two parallel lines are marked out and individuals between these lines are recorded.

In water sampling.

1) Give one reason why is it advantageous to study a sample.

a) Cheaperb) Fasterc) More Accurated) More Comprehensive

Information

2)Give one way of generating random numbers.

a) Fishbowl/Lots (with replacement)

b) Random Number Tablec) Random number

generator in the calculator or computer.

3) True or False: Random Selection is employed when every member of a population has an equal chance of being selected to be a member of the sample.

True

4) True or False: Cluster Sampling is a non-random sampling technique.

False.

5) A sampling technique used for granular or powdery samples.

Coning and Quartering

6) A technique used to mark out a small area as sample out of a large area.

Quadrat

7)A sampling technique where two parallel lines are marked out and individuals between these lines are recorded.

Belt Transect.

8-9) Give two considerations in water sampling.

a. Type of Water body.b. Tests to be performed on the

sample.c. Volume of sampled. Container to usee. Cleaning procedure for containerf. Water collection techniqueg. Transporting and storageh. How soon to process the

sample.

10) It is a subset of a population on which information is obtained.

Sample.