Collection of Data — Economics STD 11 Commerce — Question

Not representative of entire population: The accuracy of the samples drawn depe. In statistics population has a different meaning than what it is in general usage. Generally speaking, population refers to the number of people living in a geographical area but in statistics, it refers to the collection of all possible observations of specified characteristic of interest. It is also called universe. For example, if we wish to know likelihood of olay effects amongst women then women in age group of 30 and above who belong to upper middle class families will constitute our population. Sample refers to a part of population selected for analysis and drawing inferences about the population. The process of drawing samples is called sampling. If we selected 1000 women by using any method of sampling, it will be sample. When population consists of definite number of items, it is called definite population. On the other hand, when it consists of infinite number of items, it is called infinite population. For example, number of students in a class is a definite population but number of pollution creating vehicles is practically indefinite. Census Method: It is also called complete enumeration method. In this method data are collected of reach and every item of population. Advantages:

1. It provides information about each and every item of the population.
2. Element of bias is eliminated as results are based on each and every item.
3. It is an exhaustive survey which can be used for other purposes later as secondary data.
4. It helps to study diversity in the universe. It is especially useful in case of diverse population.
5. When items in a universe are of complex nature then it is necessary to use census method.

Disadvantages:

1. Census method requires a lot of expenditure in terms of time, effort and money.
2. It is possible only for definite population.
3. It is very time consuming.
4. It is not possible in some cases like we, can't use census method to find infection in blood of a person. A lady can't taste entire food to judge if it is cooked or not.

Suitability:Census method is useful when:

• Population size is limited.
• Population consists of diverse items.
• High degree of accuracy and reliability is required.
• Enough time and funds are available.

Sampling Method: In this method, a group of items are selected from population either o randomly or otherwise and these items are studies to draw inferences about the entire population. Samples are a subset of population.Advantages of Sample Method:

• Less Costly: Sample method is more economical than census method. It needs to collect data from a part of population and hence costs less.
• Less Time consuming: It is far less time consuming as compared to census method. Due to smaller volume of data, it takes lesser time.
• Greater Accuracy: Accuracy of sampling data is more because it involves lesser calculations and lesser handling of data.
• Scientific Approach: It is a scientific method of data collection because it does not take all items but scientifically selects such a part of population which is representative of entire population.
• Greater Scope: When we want to collect data in greater details, this method is more useful. It is also more useful when enumerators are required to collect data and help of experts is required.
• Mathematical Convenience: Sample data is mathematically easier to handle as it is small in volume.
• Exceptional Applicability: In many cases, we have only one option which is sampling method. When we want to test blood, we can take only a sample and not entire blood. Similarly, for testing your knowledge, teacher can't give the complete chapter in test but takes some questions at random which are sample for her.

Disadvantages of Sample Method:

• Difficult to achieve complete accuracy: It is almost impossible that there are no difference between results of census method and results of sampling methods. There always exist some difference which is called sampling errors.
• Bias in Sample Selection: Many a times, sample is selected in a biased way. He might have some interest in a particular interest and may modify the data accordingly. For example, if principal ask teacher to give five copies of her class, teachers used biased selection of sampling.
• Samples are ends on whether the sample is representative of the characteristics of population. Practically, no sample is proper represents entire population.
• Not possible in case of Heterogeneous Population: Sampling method cannot be used in case of heterogeneous population.
• Lack of expertise: For drawing a sample scientifically, specialized knowledge and expertise is required which is not so easily available.

Suitability:

• Sample method is useful when:
• Population is homogeneous.
• Experts are available to withdraw sample scientifically.
• Less time and money is available.
• Accuracy is not so important.