Friday, August 30, 2013

light and shadow model

1 light source through a slit ( or 2 pink blocks) , notice the shadow-umbra and the light-bright light.
http://weelookang.blogspot.sg/2013/08/refraction-model.html
Ejs Open Source Light and Shadow Model java applet
author andrew duffy, remixed by lookang
from here http://www.compadre.org/osp/items/detail.cfm?ID=9983
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_light_and_shadowwee.jar

2 light source through a slit ( or 2 pink blocks) , notice the shadow-umbra and penumbra-dark grey shadow and the light-bright light.
http://weelookang.blogspot.sg/2013/08/refraction-model.html
Ejs Open Source Light and Shadow Model java applet
author andrew duffy, remixed by lookang
from here http://www.compadre.org/osp/items/detail.cfm?ID=9983
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_light_and_shadowwee.jar
photo by msahinbulbul@gmail.com
3 sources added and its effects of umbra, penumbra and light effects
http://weelookang.blogspot.sg/2013/08/refraction-model.html
Ejs Open Source Light and Shadow Model java applet
author andrew duffy, remixed by lookang
from here http://www.compadre.org/osp/items/detail.cfm?ID=9983
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_light_and_shadowwee.jar

2 light source through a slit ( or 2 pink blocks) , notice the shadow-umbra and penumbra-dark grey shadow and the light-bright light.
http://weelookang.blogspot.sg/2013/08/refraction-model.html
Ejs Open Source Light and Shadow Model java applet
author andrew duffy, remixed by lookang
from here http://www.compadre.org/osp/items/detail.cfm?ID=9983
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_light_and_shadowwee.jar
photo by msahinbulbul@gmail.com


light and shadow model by andrew duffy and remixed version here by lookang
Ejs Open Source Light and Shadow Model java applet




2 light source nearer to each other, through a slit ( or 2 pink blocks) , notice the shadow-umbra and penumbra-dark grey shadow and the light-bright light.
http://weelookang.blogspot.sg/2013/08/refraction-model.html
Ejs Open Source Light and Shadow Model java applet
author andrew duffy, remixed by lookang
from here http://www.compadre.org/osp/items/detail.cfm?ID=9983
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_light_and_shadowwee.jar
photo by msahinbulbul@gmail.com



changes made:

  1. design with layout to my usual specification
  2. added source 3
  3. design intensity sliders, for the effect of light and shadow when the light overlap
enjoy!

GIREP representative letter 2013

GIREP representative letter http://www.unipa.it/girep2014/
http://www.unipa.it/girep2014/
attachment:

official:

PLEASE PROVIDE US WITH SOME BASIC INFORMATION/NEWS ON YOUR PHYSICS EDUCATION COMMUNITY: WE WOULD LIKE TO POST IT IN THE GIREP NEWSLETTER OF OCTOBER. SO,IF SOMETHING SPECIAL HAPPENED OR IS STILL GOING ON, DO NOT HESITATE TO LET US KNOW IN A SHORT PARAGRAPH. THANK YOU VERY MUCH!!!

Thursday, August 29, 2013

refraction model

author fu-kwun hwang, remixed by lookang
from here http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=152.0
into this http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=2832.0
http://weelookang.blogspot.sg/2013/08/refraction-model.html

for learning objectives

  1. State that waves can change direction as they cross straight boundaries between media and that this is called refraction
  2. Explain that refraction is caused by a change of speed in the media and use rules to predict which way the ray bends when density changes

http://weelookang.blogspot.sg/2013/08/refraction-model.html
Ejs Open Source Refraction Wave Model across 2 straight media java applet
author fu-kwun hwang, remixed by lookang
from here http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=152.0
https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_twomediaspeedwee3.jar
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_twomediaspeedwee3.jar

http://weelookang.blogspot.sg/2013/08/refraction-model.html when n1 = n1 (equal). no refraction occurs
Ejs Open Source Refraction Wave Model across 2 straight media java applet
author fu-kwun hwang, remixed by lookang
from here http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=152.0
https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_twomediaspeedwee3.jar
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_twomediaspeedwee3.jar

http://weelookang.blogspot.sg/2013/08/refraction-model.html when n1 = n1 (equal). no refraction occurs
Ejs Open Source Refraction Wave Model across 2 straight media java applet
author fu-kwun hwang, remixed by lookang
from here http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=152.0
https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_twomediaspeedwee3.jar
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_twomediaspeedwee3.jar

changes made include:


  1. re-layout according my usual design
  2. added second set of arrows (yellow) and dynamic text v = XXX c as it enters the medium 2
  3. made medium 1 white
  4. made drag-gable point green and remove associated slider for simpler control-layout
  5. added hint that shows h2/h1 as the ratio of n2/n1

enjoy!
another cool simulation here
http://phet.colorado.edu/en/simulation/bending-light

waves for O level physics

someone who knows me, ask for this learning objectives to be meet through open source physics!
why not benefit anyone need seeks this knowledge :)
thus, this blog post is universally accessible through internet(no passowrd nor login) for the purpose of open educational resources!
enjoy!
i wonder who is this north zone head New Zealand!! (that means another international collaboration right?) of science department that my MOE-ETD-LPET colleague Audrea Cheang is working with?



1. Define and describe waves using the terms: wavelength, amplitude, time period, frequency, wave speed, peak/crest and trough
http://weelookang.blogspot.sg/2011/04/ejs-open-source-wave-representations.html
Ejs Open Source Wave Representations Model Java Applet Simulation
https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_users_sgeducation_lookang_Wave_representations_v5.jar
author: Andrew Duffy, remixed by lookang




2. Calculate wave speed using frequency and wavelength and using distance and time 

Ejs Open Source Wave Machine Model Java Applet
http://weelookang.blogspot.sg/2012/08/ejs-open-source-wave-machine-model-java.html
author: Wolfgang Christian, this remixed version is by lookang,
v = f λ , so f = 1/T and T can be measured on the simulation, λ also can be determined, therefore v is found.
https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_WaveMachinewee.jar
customized to video here for inquiry http://www.nationalstemcentre.org.uk/elibrary/resource/2096/wave-machine

3. Define and differentiate between longitudinal and transverse waves and give examples of each including water waves, sound waves and light waves (electromagnetic waves) 
picture of Standing Wave in Pipes showing a closed closed end pipe at lowest frequency with ability to calculate with Length of pipe as a variable
uncheck closed for both ends, should be able to see transverse wave.
longitudinal wave is at the bottom
http://weelookang.blogspot.sg/2012/01/ejs-open-standing-wave-in-pipes-model.html
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_pipewee01.jar
author: Juan Aguirregabiria and lookang (this remix version)
Ejs Open Source 1 Dimension Doppler Effect Sound Wave Java Applet with features like , counters for waves emitted and detected
example of longitudinal sound wave
http://weelookang.blogspot.sg/2011/09/ejs-open-source-1-dimension-doppler.html
author: lookang based on the works on Fu-Kwun Hwang, Juan M. Aguirregabiria and Andrew Duffy
https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_users_sgeducation_lookang_dopplerxywee.jar

Ejs Open Source Propagation of Electromagnetic Wave Model Java Applet updated with wavelength showing, different implementation axes possible, side view etc
example of transverse wave (electromagnetic wave like light)
http://weelookang.blogspot.sg/2011/10/ejs-open-source-propagation-of.html
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_users_sgeducation_lookang_emwavewee.jar
author: fu-kwun hwang and lookang

4. Show that when light reflects from a surface, the angle of incidence is equal to the angle of reflection. 
Bending Light
Click to Run

5. Draw and examine the formation of virtual images in a plane mirror using two light rays 

bug fixed in convex len light travels in correct direction when image is virtual thanks to angela.teo@rgs.edu.sg
http://weelookang.blogspot.sg/2010/06/ejs-open-source-converging-diverging.html
https://dl.dropboxusercontent.com/u/44365627/lookangEJSworkspace/export/ejs_ThinLenModel02.jar
author: lookang based on the works of fu-kwun hwang



6. State that waves can change direction as they cross straight boundaries between media and that this is called refraction 

Bending Light
Click to Run

7. Explain that refraction is caused by a change of speed in the media and use rules to predict which way the ray bends when density changes 

Bending Light
Click to Run
8. Observe and describe total internal reflection

using video Snell's law of Refraction by QuantumBoffin , when i = 9.2 degree , r = 6.5 degree
http://weelookang.blogspot.sg/2012/08/snells-law-of-refractive-index.html
https://dl.dropboxusercontent.com/u/44365627/TrackerDigitalLibrarySG/TrackerQuantumBoffin/Snellslawrefractiveindex.trz
author: tracker file lookang, video QuantumBoffin


Wednesday, August 28, 2013

personal reflection on Relationships Between Parental Attachment, Work and Family Roles, and Life Satisfaction by Kristin M. Perrone*, L. Kay Webb, Z. Vance Jackson

personal reflection on Relationships Between Parental Attachment, Work and Family Roles, and Life Satisfaction by Kristin M. Perrone*, L. Kay Webb, Z. Vance Jackson
http://onlinelibrary.wiley.com/doi/10.1002/j.2161-0045.2007.tb00080.x/abstract

1. Research Question 

 to examine the relationship between
A)  IV3 parental attachment and satisfaction with IV11 work and IV12 family roles. (p1)
B) IV1 satisfaction with work(career) and marriage, IV2 parenting satisfaction, IV3 parental attachment to
DV life satisfaction.(p1)

2. IVs and DVs - 

IV = Independent Variable
IV1 satisfaction with work(career) and marriage
IV2 parenting satisfaction
IV3 parental attachment
DV life satisfaction.(p1)



3. Sample  

N = 108, (Man = 42, Woman = 66), started with 1724 in 1988


4. Research Design 

Longitudinal study via annual mailed surveys since 1988 (Q: how many years did the study take? until 1994?)


5. Data collection -  (Q1: how is the mean calculation from?)

IV2 Parental attachment 6 item 5-point likert scale survey
DV Life satisfaction 5 item 5-point likert scale survey
IV11 Work satisfaction 4 item 5-point likert scale survey
IV12 Martial satisfaction 3 item 7-point likert scale survey
IV2 Parental satisfaction 3 item
Open-ended questions
could benefit from chronological order IV1, IV2, IV3 and DV instead of jumping around.

6. Key Findings 

  1. continued attachment to mother  18.52/30 ± 4.51 & 0.67 correlation to 2 continued attachment to father 
  2. continued attachment to father       15.74/30 ± 5.16
  3. Life satisfaction 19.89/30 ± 3.37  & 0.42 correlation to 4 Work satisfaction & 0.46 correlation to Martial satisfaction & 0.34 correlation to parental satisfaction 
  4. Work satisfaction 19.99/30 ± 3.39 & 0.26 correlation to  parental satisfaction 
  5. Martial satisfaction 17.72 ± 3.32
  6. Parental satisfaction 17.24 ± 1.93
IV1 work satisfaction and martial satisfaction contribute significantly to DV life satisfaction

open ended question suggests IV3 parental attachment relationships affected participants' IV1 career(work), IV1 marriage, IV2 parenting, and DV life satisfaction in varied and complex ways

implication:

help individuals with work and martial relationships to develop strategies for improving their work and martial satisfaction as it contribute significantly to life satisfaction.


7. Strengths and Weaknesses 

Limitation: small N = 108
majority of N are caucasians

Tuesday, August 27, 2013

Physics Education Free Issue Until 21/09/2013

Another great initiative by IOPscience publishing to let their articles go free access for a month or so. Go download, it is free access for another 20+days! Another reason why I send my manuscripts to IOPscience.
enjoy!
http://iopscience.iop.org/0031-9120/48
Physics Education Free Issue Until 21/09/2013
Physics Education Free Issue Until 21/09/2013. http://iopscience.iop.org/0031-9120/48

toy car rolling down a steep and gentle slope by Ooi Junwei, Samuel.

toy car rolling down a steep and gentle slope by Ooi Junwei, Samuel.
based on lesson shared here http://ictconnection.moe.edu.sg/ict-in-action&func=view&rid=1590

Thanks to Ooi Junwei, Samuel. ooi_junwei_samuel@moe.edu.sg for sharing his video


Tracker analysis in toy car rolling down a slope
Author of video: Ooi Junwei, Samuel
Author of analysis: lookang (i had to re-track all points as the files had missing files?)

changes i had to make for the data to make sense.

  1. calibrate the height of the white board to 1 m (assumption i made)
  2. i did not change the frame rate to 400 /s, so the "time" scale is base on arbitrary units, so samuel slow down the video i think.
  3. took measurement to y = -1.17 m for both video for equal comparison
  4. time taken for steep slope = 6 units and gentle slope is 8 units
  5. therefore, steep slope motion reach y = -1.17 m earlier than gentle slope

http://weelookang.blogspot.sg/2013/08/toy-car-rolling-down-steep-and-gentle.html
https://dl.dropboxusercontent.com/u/44365627/TrackerDigitalLibrarySG/TrackerNJC/toycargentleslopefirst.trz
author: Ooi Junwei, Samuel video, analysis lookang

toy car rolling down a slope by Ooi Junwei, Samuel.

toy car rolling down a slope by Ooi Junwei, Samuel.
based on lesson shared here http://ictconnection.moe.edu.sg/ict-in-action&func=view&rid=1590
Thanks to Ooi Junwei, Samuel. ooi_junwei_samuel@moe.edu.sg for sharing his video


Tracker Modeling in toy car rolling down a slope
Author of video: Ooi Junwei, Samuel
Author of model: lookang

changes i had to make for the data to make sense.
  1. change frame rate to 400 /s i speculate Samuel's video was from a high speed camera or tracker assume it was 30 frame/s which didn't make sense.
  2. re-track motion
  3. create model
  4. tilt axes to measure down the slope as x direction
  5. analyse the data to get g and vx0
  6. fit into the model to test its validity




http://weelookang.blogspot.sg/2013/08/toy-car-rolling-down-slope-by-ooi.html
Tracker Modeling in toy car rolling down a slope is fx = -g*sin(θ), vx0 = 1.478 where g = 2*4.866 (from data analysis of x versus t and quadratic fit, coefficient A = 4.866) vx0 = 1.478 (from data analysis of vx versus t linear fit B = 1.478)
https://dl.dropboxusercontent.com/u/44365627/TrackerDigitalLibrarySG/TrackerNJC/toycarslope.trz
author: lookang model and Ooi Junwei, Samuel video
http://weelookang.blogspot.sg/2013/08/toy-car-rolling-down-slope-by-ooi.html
Tracker Modeling in toy car rolling down a slope is fx = -g*sin(θ), vx0 = 1.478 where g = 2*4.866 (from data analysis of x versus t and quadratic fit, coefficient A = 4.866)
https://dl.dropboxusercontent.com/u/44365627/TrackerDigitalLibrarySG/TrackerNJC/toycarslope.trz


http://weelookang.blogspot.sg/2013/08/toy-car-rolling-down-slope-by-ooi.html
vx0 = 1.478 (from data analysis of vx versus t linear fit B = 1.478)
https://dl.dropboxusercontent.com/u/44365627/TrackerDigitalLibrarySG/TrackerNJC/toycarslope.trz

Monday, August 26, 2013

Oscillator Chain JS Model written by Wolfgang Christian

Oscillator Chain JS Model written by Wolfgang Christian

as PhET releases their HTML5 enabled applets (see my earlier post) , OSP is also beginning to allow users to generate Java Scripts applets that runs on almost any browser except internet explorer 8 on my machine. We are all eagerly awaiting the release of EJS 5.0 that has been able to generate these applets on Java Scripts that allows any browser to run them, it should include mobile operating system such as Android (tested by me) and iOS (untested).

AWESOME!

click on this link to launch the applet on your Android or iOS devices.
https://dl.dropboxusercontent.com/u/44365627/JavaScripts/ejss_model_mech_CoupledOscillatorChain/CoupledOscillatorChain_Simulation.html

Oscillator Chain JS Model written by Wolfgang Christian
tested to work on Android Chrome
https://dl.dropboxusercontent.com/u/44365627/JavaScripts/ejss_model_mech_CoupledOscillatorChain/CoupledOscillatorChain_Simulation.html


Oscillator Chain JS Model written by Wolfgang Christian
tested to work on iOS Safari
https://dl.dropboxusercontent.com/u/44365627/JavaScripts/ejss_model_mech_CoupledOscillatorChain/CoupledOscillatorChain_Simulation.html





taken from http://www.compadre.org/osp/items/detail.cfm?ID=12977&S=2

Coupled Oscillator Chain

"The investigation by John and Daniel Bernoulli [of the coupled oscillator chain] may be said to form the beginning of theoretical physics as distinct from mechanics, in the sense that it is the first attempt to formulate the laws of motion of a system of particles rather than that of a single particle." Leon Brillouin

Oscillator Chain models a one-dimensional linear array of coupled harmonic oscillators with fixed ends. This model can be used to study the propagation of waves in a continuous medium and the vibrational modes of a crystalline lattice. The Ejs model shown here contains 31 coupled oscillators equally spaced within the interval [0, 2 π] with fixed ends. The m-th normal mode of this system can be observed by entering f(x) = sin(m*x/2) as the initial displacement where m is an integer.

Wave propagation can be studied by entering a localized pulse or by setting the initial displacement to zero and dragging oscillators to form a wave packet. An interesting and important feature of the Oscillator Chain model is that the speed of a sinusoidal wave along the oscillator array depends on its wavelength. This causes a wave packet to disperse (change shape) and imposes a maximum frequency of oscillation (cutoff frequency) as is observed in actual crystals.

References:

The coupled oscillator (beaded string) model is discussed in intermediate mechanics textbooks.
Analytical Mechanics 5 ed by Grant R. Fowles and George L. Cassiday, Saunders College Publishing (1993)

There are many laboratory and computer experiments that build on the basic model.
"Normal modes and dispersion relations in a beaded string: An experiment for an undergraduate laboratory,"
Gauri Shanker, V. K. Gupta, N. K. Sharma, and D. P. Khandelwal, Am. J. Phys.53, 479 (1985)
"One-dimensional lattice dynamics with periodic boundary conditions: An analog demonstration,"
Jon H. Eggert, Am. J. Phys. 65, 108 (1997)
"Evolution of a vibrational wave packet on a disordered chain," Philip B. Allen and Jonathan Kelner,
Am. J. Phys. 66, 497 (1998)

Credits:

The Oscillator Chain JavaScript Model was developed by Wolfgang Christian using version 5 of the Easy Java Simulations (EJS 5) modeling tool. Although EJS is a Java program, EJS 5 creates stand alone JavaScript programs that run in almost any browser. Information about EJS is available at: <http://www.um.es/fem/Ejs/> and in the OSP comPADRE collection <http://www.compadre.org/OSP/>.


Theory: by professor wolfgang christian

Oscillator Chain Model

Let yi= y(xi,t) represent the time-dependent displacement of a particle of mass M with horizontal position xi. Each particle is coupled to its nearest neighbors with a spring in order to form a chain of oscillators. It is assumed that the particles move only in the y-direction and that the force Fi on the i-th particle depends on the relative displacement between that particle and its nearest neighbors. The force on the i-th particle can be written as

Fi = -K [ ( y i+1- y)-( yi-yi-1)]

where K is the Hook's law coupling constant. Because the first and last particles in the lattice are fixed, we compute particle accelerations starting with the second particle and continuing through the lattice until we reach the next-to-last particle. This, the particles in a chain with N oscillators are labeled [0, 1, 2, .... N-1, N, N+1].

One way of understanding a chain of N coupled oscillators of length L and mass M is to study the motion of its normal modes. A normal mode is a special configuration (state) where every particle moves sinusoidally with the same angular frequency ωm. The m-th mode Φm of the oscillator chain of length L is

Φm ( x,t) = sin ( m π x / L) cos ( wm t+ φ )

The system stays in a single mode and every particle oscillates with constant angular frequency ωm if the oscillator chain is initialized in a single mode.

wm^2 = 4K/M sin^2( mπ / 2N)

An arbitrary initial configuration can be expressed as sum of these normal modes.

Java Scripts Half Atwood Machine Applet that runs on Android by Wolfgang Christian

exciting Java Scripts stuff from Wolfgang Christian that runs on Android.
http://www.compadre.org/osp/items/detail.cfm?ID=12976

i am hoping it is generated by EJS and yes it is. EJS 5.0.

https://dl.dropboxusercontent.com/u/44365627/JavaScripts/HalfAtwoodMachine_Simulation.html
click this link to see and play with the simulation shown below

https://dl.dropboxusercontent.com/u/44365627/JavaScripts/HalfAtwoodMachine_Simulation.html
click on link above to run simulation
Half Atwood Machine JS Model by Wolfgang Christian


this is taken from the http://www.compadre.org/osp/items/detail.cfm?ID=12976&S=2

Half Atwood Machine


The Half-Atwood Machine JavaScript Model shows a mass on a table that is accelerated by a second hanging mass. The Atwood machine (or Atwood's machine) was invented in 1784 by Rev. George Atwood as a laboratory experiment to verify the mechanical laws of motion with constant acceleration. The ideal Atwood Machine consists of two objects of mass m1 and m2, connected by an massless string over an ideal massless pulley. The half Atwood machine is a variation of that device.

Atwood's machines are a common classroom demonstration used to illustrate principles of classical mechanics because the equations of motion are easy to derive.

Credits:

The Half Atwood Machine JavaScript Model was developed by Wolfgang Christian using version 5 of the Easy Java Simulations (EJS 5) modeling tool. Although EJS is a Java program, EJS 5 creates stand alone JavaScript programs that run in almost any browser (test on Chrome Android, desktop internet browser 8 didn't work). Information about EJS is available at: <http://www.um.es/fem/Ejs/> and in the OSP ComPADRE collection <http://www.compadre.org/OSP/>.


internet explorer 8 fail

input X = t for graphs in EJS

input X = t for graphs in EJS.
http://www.compadre.org/osp/bulletinboard/TDetails.cfm?ViewType=2&TID=2727&CID=62781&#PID62804

help a user Wallace Barbosa on OSP !
input X = t for graphs in EJS

Wednesday, August 21, 2013

Research Gate looks cool

see what i being doing tonight
https://www.researchgate.net/profile/Loo_Kang_Wee/
Follow me on ResearchGate
https://www.researchgate.net/profile/Loo_Kang_Wee/?ev=hdr_xprf

https://www.researchgate.net/profile/Loo_Kang_Wee/?ev=hdr_xprf

experimental research designs

thanks to imelda and helen for sharing!

http://bloomtimes.com/2013/04/the-defeat-of-measuring-impact/
“not everything that counts can be counted, and not everything that can be counted counts”.Albert Einsteinthis is one of the best arguments for non-experimental designs in social-educational research. :)
what do you think?
https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-ash4/264502_594610043890785_1976773815_n.jpg
photo by DatosClaros - New Market Research
“not everything that counts can be counted, and not everything that can be counted counts”.Albert Einstein
this is one of the best arguments for non-experimental designs in social-educational research. :)
what do you think?



http://weelookang.blogspot.sg/2013/08/quantitative-research-methods.html
the following are my simplified reflections from C. Moorhead and imelda's notes.

The "One-Shot Case Study"

Treatment
Post-test
X
O

No control group. This design has virtually no internal or external validity.

WEAK 2 non-random, nonequivalent 2 Groups, Post-test Comparison

                                                 Treatment
Post-test
Experimental group = E            X
O
Control Group = C 
O

The main advantage of this design is randomization. The post-test comparison with randomized subjects controls for the main effects of history, maturation, reactivity and pre-testing; because no pre-test is used there can be no interaction effect of pre-test and X. Another advantage of this design is that it can be extended to include more than two groups if necessary.

WEAK 1 One group Pre-test, Post-test

Pre-test
Treatment
Post-test
O
X
O

Minimal Control. There is somewhat more structure, there is a single selected group under observation, with a careful measurement being done before applying the experimental treatment and then measuring after. This design has minimal internal validity, controlling only for selection of subject and experimental mortality. It has no external validity. Useful for exploratory purpose

WEAK 3 Two groups, Non-random Selection, Non-equivalent, Pre-test, Post-test

Group
Pre-test
Treatment
Post-test
Experimental group = E
O
X
O
Control Group = C
O

O

The main weakness of this research design is the internal validity is questioned from the interaction between such variables as selection and maturation or selection and testing. In the absence of randomization, the possibility always exists that some critical difference, not reflected in the pretest, is operating to contaminate the posttest data. For example, if the experimental group consists of volunteers, they may be more highly motivated, or if they happen to have a different experience background that affects how they interact with the experimental treatment - such factors rather than X by itself, may account for the differences.

STRONG 1 Two groups, Random Selection, Equivalent, Pre-test, Post-test

Group
Pre-test
Treatment
Post-test
Experimental group = E (R)
O
X
O
Control Group =C (R)
O

O

The advantage here is the randomization, so that any differences that appear in the posttest should be the result of the experimental variable rather than possible difference between the two groups to start with. This is the classical type of experimental design and has good internal validity. The external validity or generalizability of the study is limited by the possible effect of pre-testing. The Solomon Four-Group Design accounts for this.For controls for the main effects of history, maturation, testing effect, instrumentation, reactivity, regression to mean, selection bias.

STRONG 2 Two groups, Non-Random Selection, Equivalent, Post-test

Group
Pre-test
Treatment
Post-test
Experimental group = E (R)

X
O
Control Group =C (R)


O

This is the classical type of experimental design and has good internal validity. The external validity or generalizability of the study is limited by the possible effect of pre-testing. The Solomon Four-Group Design accounts for this.For controls for the main effects of history, maturation, testing effect, instrumentation, reactivity, regression to mean, selection bias.



STRONG 3 Solomon Four-Group Random Selection Design

Group
Pre-test
Treatment
Post-test
Pre-tested Experimental Group = E (R)
O
X
O
Pre-tested Control Group = C (R)
O

O
Unpre-tested Experimental Group = UE (R)

X
O
Unpre-tested Control Group = UC (R)


O

This design overcomes the external validity weakness in the above design caused when pre-testing affect the subjects in such a way that they become sensitized to the experimental variable and they respond differently than the unpre-tested subjects.For controls for the main effects of history, maturation, testing effect, instrumentation, reactivity, regression to mean, selection bias.

QUASI 1 Two groups, Non-Random Selection, Non-Equivalent, Pre-test, Post-test

Group
Pre-test
Treatment
Post-test
Experimental group = E (R)
O
X
O
Control Group =C (R)
O

O

The advantage here is the randomization, so that any differences that appear in the posttest should be the result of the experimental variable rather than possible difference between the two groups to start with. This is the classical type of experimental design and has good internal validity. The external validity or generalizability of the study is limited by the possible effect of pre-testing. The Solomon Four-Group Design accounts for this.For controls for the main effects of history, maturation, testing effect, instrumentation, reactivity, regression to mean, selection bias. I am using this sometimes. When well-designed and executed can yield comparable effect size.








reference: by C. Moorheadhttps://www.google.com.sg/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDIQFjAA&url=http%3A%2F%2Fwww.dartmouth.edu%2F~oir%2Fdocs%2FTypes_of_Experimental_Designs_Handout.doc&ei=anwUUpiuM8nsrAf6uoHAAQ&usg=AFQjCNE9W2ZgXBiGa5Nd_FXRK5sP5Sq-Tg&sig2=1DmlpQ4cMgySMEEhE70pyA&bvm=bv.50952593,d.bmk