Wednesday, April 28, 2010

Different types of Sampling Method

Sampling Methods:-
1) Probability Sampling Method
2) Non-Probability Sampling Method

Probability Sampling Methods –
1) A simple random sample:- A simple random sample is obtained by choosing elementary units in search a way that each unit in the population has an equal chance of being selected. A simple random sample is free from sampling bias. However, using a random number table to choose the elementary units can be cumbersome. If the sample is to be collected by a person untrained in statistics, then instructions may be misinterpreted and selections may be made improperly. Instead of using a least of random numbers, data collection can be simplified by selecting say every 10th or 100th unit after the first unit has been chosen randomly as discussed below. Such a procedure is called systematic random sampling.

2) A stratified sample:- A stratified sample is obtained by independently selecting a separate simple random sample from each population stratum. A population can be divided into different groups may be based on some characteristic or variable like income of education. Like anybody with ten years of education will be in group A, between 10 and 20 group B and between 20 and 30 group C. These groups are referred to as strata. You can then randomly select from each stratum a given number of units which may be based on proportion like if group A has 100 persons while group B has 50, and C has 30 you may decide you will take 10% of each. So you end up with 10 from group A, 5 from group B and 3 from group C.

3) A cluster sample:- A cluster sample is obtained by selecting clusters from the population on the basis of simple random sampling. The sample comprises a census of each random cluster selected. For example, a cluster may be something like a village or a school, a state. So you decide all the elementary schools in New Delhi are clusters. You want 20 schools selected. You can use simple or systematic random sampling to select the schools, and then every school selected becomes a cluster.

Non Probability Sampling Methods –

1) Convenience Sampling:- Where the researcher questions anyone who is available. This method is quick and cheap. However we do not know how representative the sample is and how reliable the result.

2) Quota Sampling:- Using this method the sample audience is made up of potential purchasers of your product. For example if you feel that your typical customers will be male between 18-23, female between 26-30, then some of the respondents you interview should be made up of this group, i.e. a quota is given.

3) The judgement sample:- A judgement sample is obtained according to the discretion of someone who is familiar with the relevant characteristics of the population.


Wednesday, April 21, 2010

How To Get Good Pictures - The Rule of Thirds

One of the most popular 'rules' in photography is the Rule of Thirds. It is also popular amongst artists. The Rule of Thirds is based on the fact that the human eye is naturally drawn to a point about two-thirds up a page. It is a compositional rule of thumb in visual arts such as painting, photography and design.

The rule states that an image should be imagined as divided into nine equal parts by two equally-spaced horizontal lines and two equally-spaced vertical lines, and that important compositional elements should be placed along these lines or their intersections. Proponents of the technique claim that aligning a subject with these points creates more tension, interest and energy in the composition than simply centering the subject would.

The rule of thirds is applied by aligning a subject with the guide lines and their intersection points, placing the horizon on the top or bottom line, or allowing linear features in the image to flow from section to section. The main reason for observing the rule of thirds is to discourage placement of the subject at the center, or prevent a horizon from appearing to divide the picture in half. When photographing or filming people, it is common to line the body up with a vertical line, and having the person's eyes in line with a horizontal one. If filming a moving subject, the same pattern is often followed, with the majority of the extra room being in front of the person (the way they are moving).

Reference :-


Wednesday, April 14, 2010

Characteristics of Camera Lens

-Focal length: Light rays which are parallel to the axis of the lens, after passing through a convex lens meet at a point on the other side of the lens. This point is called as a focus of the lens. The distance between focus and the optical centre (or node) of the lens is called as focal length of that lens. Focal length of a camera lens may also be defined as the minimum practicable distance between film/image sensor and (the optical centre of) the lens. Focal length of a camera lens is usually marked in mm on the front of the lens. Focal length remains fixed for a given lens (other than zoom lens). SLR camera may take lenses having different focal lengths.

-Angle of View: The angle through which a scene is recorded on the film/sensor. The angle of coverage of a photograph. Angle of view varies with focal length. Smaller the focal length, wider the angle of view and vice versa. Angle of view is measured diagonally.

-Lens Elements: A camera lens is generally a combination of a number of glass pieces called as lens elements. Such lens is called as a compound lens and its final effect is similar to a single convex lens. Camera lenses are designed and manufactured with utmost care using superior optical glass. One should choose lens with least lens elements

-Lens Coating: Every lens element is coated with a very thin layer of some chemical to avoid internal reflections and scattering of light resulting from various surfaces of the lens elements. These internal reflections reduce image contrast and the resulting image looks dull. Lens coating minimizes this effect and improves the image quality. Lens coating are very delicate and have to be preserved with proper care.Cleaning/wiping of lens damages these coatings to some extent.

-Speed of Lens: Highest transmitting power of the lens. It is usually denoted in terms of the f-number of the widest practical aperture of the lens. Fast lenses make photography possible in poor light conditions and are also helpful in getting a bright viewfinder image in SLR camera.


Wednesday, April 7, 2010

Benefits of Advertising

1. Economic Benefits of Advertising: Advertising can play an important role in the process by which an economic system guided by moral norms and responsive to the common good contributes to human development. Advertising can be a useful tool for sustaining honest and ethically responsible competition that contributes to economic growth in the service of authentic human development. Advertising does this, among other ways, by informing people about the availability of rationally desirable new products and services and improvements in existing ones, helping them to make informed, prudent consumer decisions, contributing to efficiency and the lowering of prices, and stimulating economic progress through the expansion of business and trade. All of these can contribute to the creation of new jobs, higher incomes and a more decent and humane way of life for all.

2. Cultural Benefits of Advertising: Because of the impact advertising has on media that depend on it for revenue, advertisers have an opportunity to exert a positive influence on decisions about media content. This they do by supporting material of excellent intellectual, aesthetic and moral quality presented with the public interest in view, and particularly by encouraging and making possible media presentations which are oriented to minorities whose needs might otherwise go unserved. Moreover, advertising can itself contribute to the betterment of society by uplifting and inspiring people and motivating them to act in ways that benefit themselves and others.

3. Moral and Religious Benefits of Advertising: In many cases too benevolent social institutions, including those of a religious nature, use advertising to communicate their messages - messages of faith, of patriotism, of tolerance, compassion and neighbor service of charity toward the needy, messages concerning health and education, constructive and helpful messages that educate and motivate people in a variety of beneficial ways.


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