Types Of Probability Sampling

 Probability sampling is characterized by an element of chance and likelihood where every element of the population of interest has known and equal probability of being selected. But it does not mean that we know in advance which element will be selected next. In other words, no one can anticipate precisely that a particular element will be selected next. Probability sampling is considered to be the most reliable and dependable kind of sampling in the field of research. Since the element of biasness is very small or even zero in this kind of sampling. Following are the well known types of Probability Sampling.

1. Simple Random Sampling:

In simple random sampling there is an equal chance for every member of the population to be selected for the sample. When sampling in this way, we make a list of all the elements of the population of interest, then we randomly select elements from this list—Sampling Frame. Simple random sampling is used when we don’t have any prior knowledge about the distribution of the characteristic of interest across the population. Example: Random selection of 30 students from a class of 70, is an example of simple random sampling. Since there are 70 students in this class—sampling frame, wherein each student has an equal chance of being selected i.e. It’s probability of selection is 1/70.

2. Stratified Random Sampling:

 In stratified random sampling we divide all the elements of the population of interest into different subgroups in such a way that they will be homogenous within groups and heterogeneous among groups. In other word all the strata will be disjoint and non-overlapping so that putting them together will make the population of interest. We then randomly select elements from each of these subgroups—strata. This kind of sampling is used when we know that the characteristic of interest is not equally distributed across the population, and its density and occurrence is different in different parts of the population of interest. It means that we should have prior knowledge about the distribution of the characteristics of interest in the population when using this type of sampling.

There are two types of stratified sampling which are given as under:

2.1 Proportional Stratified Sampling:

In proportional stratified sampling we select elements from each subgroup—stratum—according to their proportion in the population of interest. For example if we want to know public opinion about a certain national issue of a country whose population is divide into four ethnics groups as under:

Muslims = 40%

Christians = 30%

Hindus = 20%

Buddhists = 10%

Now, If we want to draw a sample of 1000 persons from the population , then, according to the proportional stratified sampling, the composition of our sample would be:

Muslims = 40/100 × 1000 = 400

Christians = 30/100 × 1000 = 300

Hindus = 20/100 × 1000 = 200

Buddhists = 10/100 × 1000 = 100

2.2. Disproportional Stratified Sampling:

In a disproportional stratified sampling we randomly select elements from the given strata not according to its ratio in the population of interest but according to our will or need.

3. Cluster Sampling:

Sometimes our population is consisted of different clusters i.e. schools, hospitals, industries etc. If we randomly select some cluster from the given population then it is called cluster sampling. Cluster sampling can be done in the following two ways:

3.1. Single Stage Cluster Sampling:

In single stage cluster sampling all the elements of a cluster are selected as a sample.

3.2. Two Stage Cluster Sampling:

In two stage cluster sampling, first we randomly select some clusters from the given population, then some elements from each cluster are randomly selected.

4.  Stratified Cluster Sampling:

In order to minimize the occurrence of errors in cluster sampling, a new variety of cluster sampling has been introduced by combining stratified and cluster sampling which is called Stratified Cluster Sampling. In this kind of sampling, all the clusters having similar characteristics are stratified together and then at least one cluster is randomly selected from each stratum. After that either all or some elements of each selected cluster are sampled.

5.  Systematic Sampling:

Unlike simple random sampling, in systematic sampling the selection of elements from a population— sampling frame— is not random, except the first element, but systematic. In systematic sampling we put all the elements of a population in such a sequence where every element has an equal chance of being selected. Then we divide this sequence in several groups of k elements each. In other words, to select a systematic sample of size n from a sample frame of size N, we divide N by n to get k. Then, we randomly select the first element (n1 )from the first group of k elements and then use the following rule.
  k = N/n
  First elements = n1
  Second element = n1 + k = n2 
  Third element = n2 + k = n3 and so on.
Suppose N =20 and n = 5 then k = 20/5=4. Now we randomly select the first item from the integers 1 to 4. If the random number selected is 3, then our systematic sample will contain the elements 3, 3+4 = 7, 7 + 4 = 11, and so on until we have 5 elements in our sample.

6. Multi-Stage Sampling:

Multi-stage sampling is a process which involves several stages. First, the larger population is divided in different clusters, then all the clusters are divided in various groups—strata— according to their characteristics i.e. clusters with similar characteristics are grouped together. Next one or more clusters are randomly selected from each stratum. Then the selected clusters are further divided in smaller clusters. This process continues in the top down direction dividing bigger clusters into smaller clusters until they cannot be divided anymore. And finally individual unites are selected from each cluster. For example, a country is divided into different geographic areas i.e. states, cities, urban and rural. Than all the areas with identical characteristics are combined together to form one stratum. And in this way several strata are made.

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Defense Mechanisms As Described By Freud

Defense Mechanisms consists of those techniques which are used by our Ego to protect us from anxiety, and to keep us psychologically healthy. As already mentioned, the job of Ego is to meet the demands of Id and Super Ego. But sometime, it is not possible for Ego to keep them both happy. If he keeps one happy the other will become angry and vice versa. To resolve this problem, Ego searches for an alternative solution. But, if it fails in finding a real solution, it will resorts to a false solution of the problem, because it does not want to bring the issue into the notice of our conscious. So it deceives our conscious and pretends that nothing has happened. In fact, Ego plays this illegal role for the sake of our psychological health. Hence we should thank our Ego. Following are some of the defense mechanisms which are used by our Ego.

Rationalization:

Rationalization is a technique which we use when we confront with failure in doing/achieving something. For example if I fails a screening test for a job. And someone ask me, “Why did you fail in the test? My possible answer would be that the questions were irrelevant. But it may not be true, because most of the candidates have passed in the same test. In fact, I am rationalizing my bad performance in the test by making false excuses. So I put all the responsibility on the shoulder of the examiner, just to prove myself innocent, and to protect myself from the resultant anxiety.

Projection:

This defense mechanism takes place when we think that other people have the same feelings as ours. In other words, we are projecting our undesirable feelings onto others. For example if I think that people hate me, while in fact, I hate myself. Similarly, if I say that a certain friend of mine is jealous of me, while in fact, I am jealous of him. Then, I am projecting my undesirable feelings onto my friend. This technique protects us from the feelings of guilt, thereby relieve our anxiety.

Sublimation:

Sublimation is a process of converting your unpleasant feeling into something creative or positive. For example when you are angry with someone, you may do vigorous exercise.  In fact, you are redirecting your anger towards positive activity, doing exercise. Sublimation sometimes, results in creative activities like poetry, painting and composing etc.  

Reaction Formation:

Reaction Formation takes place when we begin to react against our objectionable desires. For example if I have strong desire for alcohol but I think that it is not good for my health, so I begin to hate alcohol. Put simply, when we do just opposite of what we want to do, then we are using the Reaction Formation Mechanism.

Displacement:

Displacement is a technique through which we redirect our feelings from the target person or thing towards another person or thing.  For example when you are frustrated by your boss, you may go home and kick your pet dog, or bit your family member etc. In displacement we divert our feelings from the target to the substitute.

Denial:

When we are not ready to accept the ground reality about something undesirable, we are using the denial mechanism. For example if I am smoking addict and I know that smoking is injurious for heath, but I don’t accept this fact. Then I am using denial mechanism. In fact, I am deceiving my conscious. I do this because I want to safeguard myself against the feelings of guilt and shame.

Regression:

Regression means going back to an earlier or less mature position. This happens when you are under severe stress or pressure. For example when you are hurt or frightened you may cry or scream loudly. Similarly when you are under severe stress you may frown, suck your thumb, bite your finger’s nail, pout your lower lip etc.

The psychoanalytic theory is a pioneer of modern personality theories. Since it is based on the case studies of Freud’s patients, not on empirical evidences, therefore many theorists have criticized it on the grounds that its validity can’t be measured through modern scientific tools. Another criticism on this theory came from feminists who are of the view that this theory is male oriented.

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