Powerpoint presentation - Experimental Design Used in Rice Research

Presentation Title Goes Here

…presentation subtitle.Introduction to Experimental Designs

Violeta Bartolome

Senior Associate Scientist-Biometrics

Crop Research Informatics Laboratory

International Rice Research Institute

:: color, composition, and layout

TWO TYPES OF EXPERIMENTS

• Single Factor Experiments - several levels of one

factor are being tested while keeping all other factors

at a constant level.

Example: Varietal trial - several varieties are tested

under uniform management and cultural practices.

• Multi-factor or factorial experiments - test two or

more factors simultaneously.

Example: Testing five varieties under four

nitrogen rates.


Experimental designs applicable

to single-factor experiments

• Complete Block Design (completely randomized, randomized complete block and latin square designs).

o generally used for experiments with a smallnumber of treatments.

o characterized by blocks, each of which contains the complete set of treatments.

• Incomplete Block Designs (lattices, alpha-lattice, and group balanced block designs).

o generally used for experiments with a largenumber of treatments.

o characterized by blocks, each of which contains only a fraction of the treatments to be tested.


Completely Randomized Design (CRD)

• Appropriate only for experiments with no obvious

heterogeneity between experimental units.

• Any difference among experimental units receiving

the same treatment is considered as experimental

error.

• Treatments are assigned completely at random so

that each experimental unit has the same chance of

receiving each of the treatments.


A field experiment is to be conducted in CRD with 5

treatments and 4 replications. How do you make the

layout?

Near homogeneous area:: color, composition, and layout

Step1: Divide

the area into 5

trts x 4 reps = 20

plots.


In CRD, the treatments are assigned completely at random

T1 T4 T3 T5

T3 T2 T5 T1

T4 T2 T1 T3

T1 T5 T4 T2

T2 T5 T3 T4

Step2: On 20

pieces of paper,

write treatment

numbers and put

in box.

Step3: Assign

treatment on

each plot by

drawing lots.


Randomized Complete Block Design

(RCB)

• When the experimental units are not homogeneous and it is

possible to group the experimental units into blocks such that

experimental units within each block are more homogeneous

than those between blocks.

• The presence of blocks, each containing all the treatments, is

the primary distinguishing feature of the RCB design.


An experiment is to be conducted in RCB with 5

treatments and 4 replications. How do you make

the layout?fertility gradient


fertility gradient

Block I Block II Block III Block IV

T4

T1

T3

T2

T5

T5 T2 T4

T3 T3 T5

T1 T5 T3

T4 T4 T1

T2 T1 T2

First, divide the field into 4 equal parts, each part representing one block.

Next, divide each block into 5 equal parts, each part representing one plot.

Then randomly assign the 5 treatments to the 5 plots in each block.


CRD ERROR

Block

Variation

RCBD ERROR

Experimental error is minimized by

removing block variation from the error.

Advantage of RCB


Latin Square

• Capacity to simultaneously handle two known

sources of variation.

• A treatment appears only once in each row or

column.

• To randomize, use basic plans found in some

statistics book.

• Number of treatments should be equal to number of

replications.

• Very seldom used in agricultural experiment.


Example of LATIN SQUARE layout

fertility gradient

Row 1

Row 2

Row 3

Row 4

Column 1 Column 2 Column 3 Column 4

T1 T2 T4 T3

T3 T4 T1 T2

T2 T1 T3 T4

T4 T3 T2 T1


Advantage of Latin Square

Block

Variation

RCBD ERROR

Experimental error is minimized by

removing row and column variations

from the error.

Row

Variation

Column

Variation

Latin Square Error


FACTORIAL EXPERIMENTS

Two or more factors are tested simultaneously.

Example:

2 levels of Variety (V1, V2)

3 levels of Land Preparation (L1, L2, L3)

The treatments are:

V1L1 V1L2 V1L3

V2L1 V2L2 V2L3


Advantages of factorial experiments

• Provide for examination of interaction

among the various factors tested.

• Economical by comparison to several single factor

experiments.

• Broadens applicability of main effect

conclusions.


Designs Applicable To Factorial

Experiments

• Completely Randomized Design

• Randomized Complete Block Design

• Latin Square Design

• Split Plot Family of Designs

• Strip Plot Family of Designs


An experiment involving 5 N-rates and 4 Varieties is to be conducted

in a RCB design in 3 replications. How do you make the layout?

V2

60

V4

30

V3

90

V1

120

V4

60

V2

120

V3

90

V1

60

V3

60

V1

120

V4

120

V2

90

V4

90

V2

30

V1

60

V3

0

V3

0

V1

120

V4

120

V2

0

V2

120

V1

0

V3

30

V1

90

V3

30

V4

120

V2

0

V3

120

V2

30

V3

120

V2

30

V3

120

V2

0

V4

30

V3

120

V4

0

V1

30

V2

120

V4

0

V2

90

V1

30

V2

90

V3

60

V1

90

V4

30

V2

60

V3

0

V1

30

V4

60

V1

90

V3

60

V1

0

V4

0

V2

60

V4

90

V3

30

V1

60

V4

90

V2

30

V3

90

Block 1 Block 2 Block 3


Split-Plot Design

• Has two plot sizes: the larger one is called mainplot and the smaller one subplot.

• Precision for the comparison of the subplot treatments is

expected to be higher than that for the mainplot treatments.

• Smaller difference can be detected among subplot treatments

than among mainplot treatments.


An experiment involving 5 N-rates and 4 Varieties is to be conducted in a

Split-plot design in 3 replications. How do you make the layout?

30

60

90

0

120



An experiment involving 5 N-rates and 4 Varieties is to be conducted in a

Split-plot design in 3 replications. How do you make the layout?

30

0

60

60

90

120

90

30

0

0

120

0

120

60

30

Block 1 Block 2 Block 3 :: color, composition, and layout


30

60

90

0

120

0 60

90 120

30 90

120 0

60 30


V2

V3

V1

V4


30 0 60

60 90 120

90 30 90

0 120 0

120 60 30


V2

V3

V1

V4

V4

V2

V1

V3

V2

V3

V4

V1

V3

V4

V2

V1

V3

V4

V2

V1

V4

V3

V2

V1

V2

V1

V4

V3

V4

V1

V3

V2

V1

V4

V3

V2

V4

V3

V2

V1

V2

V3

V4

V1

V3

V2

V1

V4

V1

V2

V3

V4

V1

V2

V4

V3

V4

V1

V3

V2


30 0 60

60 90 120

90 30 90

0 120 0

120 60 30


Possible Reasons for Using Split-Plot

• Management requirement: some treatments such as

water management is easier to manage in bigger

plot.

• Insertion of an additional factor into an established

experiment.

• Need to increase precision on the effect of one factor

at the expense of another.


Strip-Plot Design

• Higher degree of precision is given to the

measurement of the interaction effect than main

effects.

• Horizontal and vertical plots are perpendicular to

each other. There is no relationship between their

sizes.

• Can accommodate two mechanical factors.


Suppose an experiment involving 5 N-rates and 4 Water Levels is to be

conducted in a Strip-plot design in 3 replications. How do you make the

layout?

30

120

90

0

60

Block 1 Block 2 Block 3 :: color, composition, and layout

Suppose an experiment involving 5 N-rates and 4 Water levels to be

conducted in a Strip-plot design in 3 replications. How do you make the

layout?

30

90

0

120

60

30

90

30

60

0

120

120

60

0

90




30 90 0

120 60 30

90 30 60

0 120 120

60 0 90

W1 W3W4 W2



30 90 0

120 60 30

90 30 60

0 120 120

60 0 90

W1 W3W4 W2 W3 w4 W1 W2 W3 W2

W1 W4

Powerpoint presentation - Experimental Design Used in Rice Research

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