The success or failure of an investigation usually depends on the design of the

experiment.

Prepared byOdyssa NRM Molo

A description of what a researcher would like to find out and how to find it out.

The background information can be used as a guide.

• Complete sequence of steps or procedures that need to be followed when obtaining the needed data during investigation.

• Serves as a guide during the actual experimentation.

• Minimizes the cost of experimentation while maximizing the gathered info relevant to the problem.

• Validates the statistical test.

Subject of the study Variables Controls Experimental & control groups Instruments & devices to be used Statistical tools needed for analysis

• Main material being used in the experiment• Also called experimental unit• Can be a person, an animal, a plot in a field,

a plant, a leaf or a model of a device.• Can be subjected to different treatments

depending upon the objectives of the study– Treatment denotes any procedure done on the

experimental unit which will then be measured & analyzed.

Replication Randomization Local control Control of extraneous variables

– Experiment should be repeated several times to find an estimate of variations among observations on the groups of subjects treated alike.

– Allows the researcher to assess the significance of the observed differences

– Refers to the assignment of the experimental subjects to the treatments by chance.

– It is done to create equivalent groups prior to experiments; average out differences among groups; reduces possible bias; assures valid estimate of population parameters & statistical test of significance

Done when balancing, grouping and blocking of experimental units are employed in adopted design.

Identical conditions must be provided for the control & experimental groups. These 2 groups should differ only in terms of the absence (control) or presence of the treatment (experimental)

Completely Randomized Design (CRD)

Randomized Complete Block Design (RCBD)

• Treatments are assigned randomly to the experimental subjects without restriction.

• Experimental subjects should be homogenous with respect to all other factors which could affect the treatment being compared if they were not controlled.

• Used specially for experiments with homogenous experimental units or in experiments where environment effects are easily controlled .

• Divides the experimental subjects into more or less homogenous groups called blocks.

• Blocking is done to make sure that the experimental subjects in a group have similar characteristics so that observed differences among the groups will be largely due to the treatments.

• Most appropriate to use if subject can be categorized according to certain characteristics like gender, age, weight, & height that can affect comparison of treatments

Ready for quiz????Yeah!!!

1) A description of what a researcher would like to find out and how to find out.

2) A complete sequence of steps or procedures that need to be followed when obtaining the needed data during an investigation.

3) The main material being used in the experiment.

4) Any procedure done on # 3 answer.5) Assignment of experimental subjects to the

treatment by chance.

6) Done when balancing, grouping & blocking of experimental units are employed in the adopted design.

7) Treatments are assigned randomly in this design.

8) Homogeneous groups9) Design where subjects are divided in

groups10) Group where treatment is absent.

11-14 Principles always present in a research design

15 – 16 Types of research designTrue or False17) CRD is characterized by blocks of equal size.18) RCBD is appropriate for use if the subjects

have the same characteristics.19) Design of an experiment depends on the type

of research being undertaken.20) Research designs minimizes cost while gaining

maximum information relevant to the problem.

Page 33, Study Guide # 2 Identify the subject/s Identify the treatment Identify the control group/s Identify the experimental group/s Identify the dependent, independent, &

extraneous variables

Caintic, Helen E and Juanita M. Cruz. (2008) Scientific Research Manual. C&E Publishing, Inc.

Brynie, Faith Hickman. (1998) Painless Science Projects. Barron’s Educational Series, Inc.