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Answer to the Question

Multi-phase sampling is useful when the frame lacks auxiliary information that could be used to stratify the population or to screen out part of the population.

It consists of several subpopulations. In this case, rather than selecting a sample randomly from the entire population, it is convenient to divide such population into subpopulations according to certain criteria. This subpopulation, grouped according to certain criteria is called strata.

When one is selecting stratified sample from the population as there are many sub- population & the group is heterogenous then, Multi phase sampling will be helpful as if the auxiliary that is the secondary information to be used for stratifying the population is not available. Multiphase sampling as mentioned in my post is in which some information is collected from the whole sample and additional information is collected, at the same time or later, from sub samples of the entire sample. So auxiliary information is also collected through multiphase sampling.

Now about the pictures, well the first one is depiction of the whole multiphase sampling process, where in the first stage there in first phase all the samples are involved & then in other phases some of the samples are involved in each phase. The second one shows how from the whole sample selected in the next phase some of the part of sample is selected for data collection.

Multiphase Sampling

• Definition:
  A sampling procedure in which some information is collected from the whole sample and additional information is collected, at the same time or later, from sub samples of the entire sample (i.e. some units provide more information than others).



• Description:
  A multi-phase sample collects basic information from a large sample of units and then, for a sub sample of these units, collects more detailed information. The most common form of multi-phase sampling is two-phase sampling (or double sampling), but three or more phases are also possible.
  
  Multi-phase sampling is useful when the frame lacks auxiliary information that could be used to stratify the population or to screen out part of the population.
  
  Example 1: Suppose that an organization needs information about cattle farmers in Alberta, but the survey frame lists all types of farms—cattle, dairy, grain, hog, poultry and produce. To complicate matters, the survey frame does not provide any auxiliary information for the farms listed there.A simple survey could be conducted whose only question is "Is part or all of your farm devoted to cattle farming?" With only one question, this survey should have a low cost per interview (especially if done by telephone) and, consequently, the organization should be able to draw a large sample. Once the first sample has been drawn, a second, smaller sample can be extracted from among the cattle farmers and more detailed questions asked of these farmers. Using this method, the organization avoids the expense of surveying units that are not in this specific scope (i.e., non-cattle farmers).

  
  Multi-phase sampling can be used when there is insufficient budget to collect information from the whole sample, or when doing so would create excessive burden on the respondent, or even when there are very different costs of collection for different questions on a survey.
  
  Example 2: A health survey asks participants some basic questions about their diet, smoking habits, exercise routines and alcohol consumption. In addition, the survey requires that respondents subject themselves to some direct physical tests, such as running on a treadmill or having their blood pressure and cholesterol levels measured.Filling out questionnaires or interviewing participants are relatively inexpensive procedures, but the medical tests require the supervision and assistance of a trained health practitioner, as well as the use of an equipped laboratory, both of which can be quite costly. The best way to conduct this survey would be to use a two-phase sample approach. In the first phase, the interviews are performed on an appropriately sized sample. From this sample, a smaller sample is drawn. This second sample will take part in the medical tests.
  
• Difference & Similarities between Multiphase & Multistage Sampling:
  Multi-phase sampling is quite different from multi-stage sampling, despite the similarities in name. Although multi-phase sampling also involves taking two or more samples, in multiplephase sampling, all samples are drawn from the same frame and at each phase the units are structurally the same. However, as with multi-stage sampling, the more phases used, the more complex the sample design and estimation will become.
  
• Merits:
  It leads to the inferences of predetermined precision based on the number of observation. It reduces error.
  
• Demerits:
  It is time consuming & costly.
  It's planning & administration is complicated.
  
  Activity: Now since you'll know what multi-phase sampling is, could you think of a merit & a demerit other than mentioned above. Write them down in the comments with proper rationale.
  
• Refernces:
  http://www.statcan.ca/english/edu/power/ch13/probability/probability.
  htm#phase
  http://am.air.org/help/NAEPTextbook/htm/dsampledesign.htm
  Books :
  Online:
  http://books.google.com/booksvid=ISBN0415195411&
  amp;id=5twk1pHwyL8C&pg=PP1&lpg=PP1&ots=MMyIeSaT
  FB&dq=louis+cohen+research+methods+in+education&sig=
  NpmMEvmfN6UB0CiWUQ75An3jTQ#PPA102,M1
  Other:
  Sankhala D.P. Research Methodology inEducation.
  

Randomness can be different!

This post is in reference to the post by Hemangi named: IS randomness only of ONE type?? at http://metca6research.blogspot.com/2007/04/is-randomness-only-of-one-type.html

Difference in random sampling

• Example 1: A researcher wants to find out the opinion of primary school teachers on the increasing amounts of size and weight of children’s’ schoolbags. She decides to carry out a survey for this purpose. Out of the 1000 primary school teachers in Mumbai, she decides to select 300 teachers randomly for her study.

The difference in this example in sampling:
The researcher in this example has chosen a survey research method.

The sample is randomly selected through simple random sampling.

In this example, the sample is selected randomly out of 1000 primary school teachers in Mumbai 300 are randomly selected. So the sample is representative of the population.

In this there is only one group

The Results of this research are generalizable to all the population of 1000 primary school teachers as random sampling is done.

• Example 2: A teacher at a university wants to find out whether there is any difference caused in the academic achievements of students after using 2 different kinds of CAI packages - one with linear interactivity and the other with non-linear interactivity. She decides to carry out the study on her own batch of 50 students. Since there are 2 kinds of CAI packages to be implemented, she makes 2 groups in the following way:She lists everyone’s names on chits, and draws one chit out of the lot and writes that name under a column named linear CAI and puts that chit aside. Then she picks another one, this time writing the name under a column named non-linear CAI. She proceeds in this way until all chits have been randomly distributed under the 2 columns and she is ready with 2 groups of students for her study.

The difference in this example in the sampling technique used is:
The reseracher here has chosen the experimental method of research.

The samples are first chosen through convinence sampling technique, & then the researcher used the simple random sampling technique in order to form 2 groups. The whole population is the sample itself.

There are 2 groups of samples.

The results of this research is generalizable only to that group.

Types of Sampling (Part 1)

This post is with refernce to the post by Hemangi, titled- Let’s get sampling! ( Friday, April 6th, 2007 )

http://metca6research.blogspot.com/2007/04/lets-get-sampling.html


Differentiation between a Simple Random Sampling & Convenience Sampling:

• Simple Random Sampling:

What is it?
In a simple random sample, the researcher must take a random sample from a population, and not have any order in which one chooses the specific individual. A simple random sample is a group of subjects (a sample) chosen from a larger group (a population). Each subject from the population is chosen randomly and entirely by chance, such that each subject has the same probability of being chosen at any stage during the sampling process.

Generalizable:
The results are generalizable, as the samples are selected randomly

& thus are the true representatives of the whole population for that research.

UN-bias selection:
It is a random selection & every individual from the selected population

has a equal chance to be selected as the sample for the research. So, it is not a bias selection.

Other name:
Also called as lottery method

• Convenience sampling:

What is it?
Sampling which involves the sample being drawn from people/items that are readily available and convenient. Only those individuals have a chance of getting selected who are easily accessible or come in contact with the researcher removing the possibility of others getting selected in the sample.

Non-Generalizable:
The researcher using such a sample cannot make generalizations about the total population from this sample because it would not be representative enough. The results of the research are applicable only to that group of sample

Bias selection:
It is a biased selection, that is, it is not random & done for the convenience of the researcher.

Other name:
Also called as accidental/ oppurtunity sampling.

The images were found at the site:
http://www.thomsonedu.com/

Connecting to the world around!

Communicating & connecting to the world around us!

Communication as we all know is the process that we can see in the above image. As we can see there is a channel that carries the message across.But is it really only this????

In this post you will find various quotes, videos & images to tell you what communication is & how should we communicate for a better communication with or without use of technologies. When we talk of technologies it is important to update ourselves as to how we can use new technologies to communicate better.

Given below are three videos which will tell you something about importance of updating oneself with the technologies.( a humorous one)
http://video.yahoo.com/video/play?vid=119381&fr=yfp-t-391
http://video.yahoo.com/video/play?vid=29530&fr=yfp-t-391
http://video.yahoo.com/video/play?vid=1075691886&fr=yfp-t-391

Thanks to Hemangi she showed us a new way to communicate & learn through blogs.

Quotes:

Ambrose Bierce:
Heaven, n.: A place where the wicked cease from troubling you with talk of their personal affairs, and the good listen with attention while you expound your own.
The Devil's Dictionary

Edward R. Murrow:
The newest computer can merely compound, at speed, the oldest problem

in the relations between human beings, and in the end
the communicator will be confronted with the old problem, of what to say and how to say it.

George Bernard Shaw:
The problem with communication ... is the illusion that it has been accomplished.

John Dewey:
There is more than a verbal tie between the words common, community, and communication.... Try the experiment of communicating, with fullness and accuracy, some experience to another, especially if it be somewhat complicated, and you will find your own attitude toward your experience changing.

Woodrow Wilson:
If I am to speak ten minutes, I need a week for preparation; if fifteen minutes, three days; if half an hour, two days; if an hour, I am ready now.

Larry King:
I remind myself every morning: Nothing I say this day will teach me anything. So if I'm going to learn, I must do it by listening.

Mark Twain:
If you have nothing to say, say nothing.

Mark Twain:
19th century US author and humorist“The difference between the right word and almost the right word is the difference between lightning and a lightning bug.”

Reference for quotes:
www.wisdomquotes.com/cat_communication.html
http://www.thinkarete.com/quotes/by_category/love/communication/

Reference for images:
http://www.myownbusiness.org/images/Technology.jpg - what do I need
http://www.michaelstamand.com/paintings/paintings_2002/images/communication.jpg - painting
http://science.uniserve.edu.au/projects/skills/jantrial/images/communication_skills_graded.jpg - communication skills

Smile on Every Face???????

Life is so strange,
Nothing is such that can be arranged.
There is so much of pain,
No realation is such from which we can gain.
Fear of all kinds prevails everywhere,
Peace can be found nowhere.
No one is true by heart,
Happiness is forced to depart.
Is any one really alive ,
Or is this world full of deads??
When will these wars & disputes end??
Will there ever be happiness around??
Or there will be always fights for ground??
How many kargils do we yet have to see??
What will our world in the future be??
Will the water in the rivers be blue or red??
Every second person found on dead bed.
Will there ever be a world full of flowers??
Or we have to live with bullet showers?
Wish the world to be a better place,
Where there is a smile on every face.....

This poem is what everyone's heart says today

AFTER THIS VERY HEAVY TO DIGEST POEM...A SMALL LITTLE JOKE.....

Image 1:
http://photos1.blogger.com/blogger/708/4059/1600/PeaceNotWarPurpleLogoStrip.0.gif
Image 2:
http://photos1.blogger.com/blogger/708/4059/1600/War%20Peace.0.jpg