Statistics: Collection Of Data – Positive And Negative Responses Explained
collection of data class 11 notes
collection of data class 11 positive and negative responses
collection of data class 11 notes sandeep garg
Statistics: Collection Of Data – Positive And Negative Responses Explained
collection of data class 11 notes
collection of data class 11 positive and negative responses
collection of data class 11 notes sandeep garg
Types of Responses
Positive Responses
Negative Responses
Collection of Data – Collection of data is the systematic process of gathering and measuring numerical information from a variety of source related to a particular problem or study. For example – if you want to know which sport is the most popular in your school, you can collect data by asking your classmates through a survey. Data can be collected through surveys, questionnaires, interviews, etc. The main aim is to get accurate and reliable information which can help in drawing correct conclusions.
Sources of collection of Data
- Primary Source – Primary source refers to the origin from which the information is collected for the very first time. Information is collected directly by the researcher or with the help of investigators. As the data collected is first hand, it is highly reliable and relevant to that specific purpose of the study. For example – suppose a teacher wants to find out how students feel about the new teaching method used in class. The teacher personally talks to students or distributes a short questionnaire to collect their opinions.
- Secondary Source – Secondary Source refers to the origin from which an investigator obtains information that has already been collected, processed, and published by someone else. For example – if a teacher wants to know the pass percentage of students in the previous academic year, then the teacher can simply refer to the school’s published annual report instead of surveying students individually.
Important Terms –
- Investigator – The person who conducts the statistical enquiry is known as Investigator.
- Enumerators – The investigator needs the help of certain persons to collect the information known as Enumerators.
- Respondents – The persons, from whom the statistical information is collected, are known as Respondents.
- Survey – Survey is a method of gathering information from individuals. The purpose of the survey is to collect data to describe some characteristics like price, quality, usefulness, popularity, honesty, etc.
Primary and Secondary Data
Primary Data – Primary data is the data which is originally collected by an investigator or agency from its source of origin for the first time for some specific purpose. For example – If it is desired to conduct an inquiry into the age group of employees in a company and if such information is collected by the investigator from the workers themselves, then such data would be termed as Primary Data.
Secondary Data – The data which is not directly collected but rather obtained from the published or unpublished sources, is known as Secondary Data. It is also known as Second Hand Data. For example – Economic Survey published by Indian Government would be secondary data for any researcher.
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Methods of Collecting primary Data
- Direct Personal Investigation (Personal Interview) – Under this method, the investigator collects data by having direct contact with the respondent and conducts on-the-spot enquiry. The investigator goes to the field personally, contact the respondents and convince them in giving the information under study.
Merits of direct Personal Investigation
- Originality – The data collected is original in character.
- Reliable and Accurate – This first hand information obtained by the investigator himself is bound to be more reliable and accurate.
- Flexibility – this method is fairly elastic as the investigator can very the nature of questions and seek different kinds of information according to the need of the situation.
Demerits of Direct Personal Investigation
- Not Suitable for wide Areas – This method is not suitable when the area of coverage is considerable wide or when many respondents are to be contacted.
- Expensive and time consuming – This method is expensive and time consuming, particularly when the field of investigation is large.
- Personal Prejudice – The basis or prejudice of investigators can affect the accuracy of data to a large extent. There is a possibility of influencing respondents.
2. Indirect Oral Investigation – Under this method, the investigator approaches third parties, who are in the possession of information about the subject of enquiry. The persons to whom these questions are put are known as witnesses. For example – Suppose we want to find out how many students of a college smoke. In this case, personal investigation may fail because students might hide the truth. So, the investigator should collect information from people close to them, like friends, teachers, relative, or neighbors, who can provide correct details.
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Merits of Indirect Oral Investigation –
- Wide Coverage – This method is suitable when the area of investigation is large.
- Economical – It is economical in terms of time, money and manpower.
- Free from Bias – this method is relatively free from personal prejudice as the information is collected from the persons who are well aware of the situation.
Demerits of Indirect Oral Investigation –
- Indirect Information – The result can be erroneous because information is obtained from other persons, not directly connected.
- Lack of Accuracy – As compared with direct personal observation, the degree of accuracy of the data is likely to be lower.
- Partiality of Witness – The persons, providing the information, may be prejudiced or biased.
3. Information from Correspondents – Under this method, local agents or correspondents are appointed and trained to collect the information from the respondents.
- Agents or correspondents collect the data by their own ways or methods and send them to the investigator.
- This method of collecting primary data is used when information at regular intervals of time is to be collected from different places.
Merits of Information from Correspondents
- Wide Coverage – this method is useful in situation where the area of investigation is very large and periodic information is to be collected from the distant places.
- Economy – It is very economical in terms of money and resources.
- Suitable for special purpose – This method is suitable for some special purpose of investigations.
Demerits of Information from Correspondents
- Lack of Originality – Original data is not obtained under this method due to lack of personal contact with the respondents.
- Lack of Uniformity – The information supplied by different correspondents often lacks homogeneity, and hence, not comparable.
- Danger of Partiality – The personal bias of the correspondents may enter the reports and to that extent, the accuracy is affected.
4. Telephonic Interviews – Under this method, data is collected through an interview over the telephone with the interviewer. Telephone interview is better in the cases where the respondents are reluctant to answer certain questions in personal interviews.
Merits of Telephonic Interviews
- Wide coverage – This method is useful for conducting enquiry over a large area.
- Economical – This method is cheaper as it requires less time, money and labour.
- Clarify doubt – It is possible to assist the respondent by clarifying the questions.
Demerits of Telephonic Interviews
- Limited use – the disadvantage of this method is access to people. This method is not possible for people who do not won telephones.
- Visual feedback is not possible – Telephone Interviews also obstruct visual reactions of the respondents, which become helpful in obtaining information on sensitive issues.
5. Mailed Questionnaire Method – Under this method, the investigator markes a questionnaire to the field of investigation and send it to the respondents, along with a covering letter, to collect information from them. A questionnaire consists of a list of questions pertaining to the investigation. Blank spaces are left for writing answers.
Merits of Mailed Questionnaire Method
- Wide Coverage – this method is used for extensive enquiries covering very wide area. It is the only method to reach remote areas.
- Economy – this method is economical as it requires less time, money and labour.
- Originality – the data are very much original because respondents are directly involved in the collection of data.
Demerits of Mailed Questionnaire Method
- Limited Scope – This method is applicable only where respondents are educated.
- Less Accuracy and Precision – Under this method, the accuracy of data cannot be testified as accurate answers may not be received if questions are difficult.
- Lack of Interest – Some respondents may not care to fill up the questionnaire. When the number of such persons who have not sent back the questionnaire is very large, it is impossible to draw correct conclusions.
6. Questionnaires Filled by Enumerators – under this method, the enumerator personally visits respondents along with a questionnaire, asks questions and note down their replies in the questionnaire in his own language.
Merits of Questionnaires Filled by Enumerators
- Wide Coverage – This technique of data collection can be used for collecting information from large number of people coming from vast areas.
- Accurate and reliable information – Since the enumerator has a direct contact with the respondents, it is possible to get accurate and reliable information.
- Better Response – The presence of the enumerator may induce the respondents in giving the information. So, chances of non-response (like in case of Mailed Questionnaire Method) are less.
Demerits of Questionnaires Filled by Enumerators
- Costly Method – This method is very expensive as expenditure on training, remuneration and conveyance are to be borne by the enumerator or the agency collecting the data.
- Time Consuming – This method is more time consuming as compared to other methods because enumerators have to visit door to door to collect data.
- Partiality – lnefficiency on the part of the enumerators coupled with personal bias may adversely affect the results of the enquiry.
Qualities of a Good Questionnaire – The following general principles should be followed while designing or drafting the questionnaire:
- Limited Number of Questions – The number of questions should be as less as possible. Long questionnaires discourage people from completing them. Only those questions which have a direct relevance to the problem be included.
- Simple and short Questions – The questions should be clear, brief, and unambiguous. The question should be framed in such a manner that their answers are specific and precise.
- Questions should be logically arranged – The questions should follow a logical sequence. For example – it will be illogical to ask a man his income before asking him whether he is employed or not.
- No Personal Questions – The questions affecting the pride and sentiments of the respondents and question pertaining to their private affaires should be avoided.
- Avoid Question required calculation – The questions relating to mathematical computations or questions which force the respondent to recollect from his memory should not be asked.
Types of Questions
- Simple Alternative Questions – These questions may be answered between two alternative such as yes or no, right or wrong, true or false. Such types or questions can be used where two clear cut alternatives exits. For example:
Do you have a Car? Yes / No
Are you interested in higher studies? Yes / No
II. Multiple Choice Questions (MCQs) – In such questions, the possible answers are printed in the questionnaire and the respondent is supposed to tick any one of them. MCQs are very easy and convenient for the respondents to answer. Such questions save time and also facilitate tabulation. For example;
How do you normally reach your office? (Tick anyohe)
(i) Walk (ii) Bus
(iii)Two-wheeler (iv) Car
III. Specific information questions – The questionnaire should start from general questions and proceed to more specific ones. This helps the respondents feel comfortable. Such questions are asked to obtain some specific information. For example:
- Are you married?
- How many members are there in your family?
IV. Open Questions – These types of questions are to be answered by the respondent in his own words. The questions should be such that it is possible to answer them in few words. Such questions leave the door open to any answer. For example ;
- How can the problem of unemployment be solved?
- Are you satisfied with your monthly income?
Sources of Secondary Data
Secondary Data is the data collected by other agencies and is used for further studies. The sources of Secondary Data can broadly be classified under two heads:
- Published Sources – There are a number of national (government, semi-government and private) organizations and also international agencies, which collect statistical data in different fields like national income, population, prices, employment, wages, export, import, etc. These reports are published on regular basis, i.e. annually, quarterly, monthly, fortnightly, and so on.
- Unpublished Sources – When data collected by someone is not published and is taken by other persons for the purpose of investigation, then such data is known as ‘Unpublished Secondary Data’. For example – reports prepared by private investigation companies. Many investigations are of private nature and their findings are not published. Such unpublished data is usually meant for the use of members only.
Precautions in the use of Secondary Data
- Reliability of the Data – The reliability of secondary data can be judged by the integrity and experience of the agency, sources of information and method of data collection used.
- Suitability for the Purpose – The investigator must ensure that the data is suitable for the purpose of enquiry. The suitability of the data is determined by investigating the nature, scope, objectives, units and terms, homogeneity, time of collection, etc. of the secondary data.
- Census and Sampling Method – The investigator should also ascertain as to what method was used in collecting the data. Sampling method may be biased depending upon the mode of selection of samples. All these need to be ascertained first before making use of the secondary data.
- Adequacy and Accuracy – It is necessary to use adequate data to avoid biases and prejudices leading to erroneous conclusions. The investigator should keep in mind the degree of accuracy maintained by each investigator.
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Census Method
When a statistical investigation is conducted wherein, the data is collected from each and every element of the population, it in known as census method.
- This method is generally adopted when area of investigation is limited and an intensive study of the population is required.
- Highly trained investigators are needed to maintain a high degree of accuracy.
Merits of Census Method
- Intensive study of population – It provides intensive and in-depth information covering many facets of the problems. For example – in a population census, not only the total number of people is counted, but information such as number of males and females, age, marital status, education, occupation, etc. are also collected.
- High degree of accuracy and reliability – Since every item of the population is observed personally, it is possible to collect highly accurate and reliable information.
- Suitability of the method – This method is suitable when different items of the population are not homogeneous. For example – When items in the population are of complex nature, then census method can provide desired results.
Demerits of Census Method
- Expensive – Since the data are obtained by observing every item of the population, it is a very expensive method of investigation, especially in case of a large population.
- Needs more time and manpower – Since a large volume of data are to be collected under census investigation, more time and manpower are needed for its collection, analysis and interpretation.
- Inapplicability – Census method cannot be applied in case of infinite population. If the study involves destruction, as in case of testing of tyres on road, census cannot be conducted.
Sampling Method
When only some representative items of a population are selected and data collected from these items are used for the analysis, the method is known as Sampling Method.
Factors Affecting Size of Sample
The following points should be kept in mind while deciding the size of sample:
- Size of Population – In case of large size of population, sample size would be bigger and vice-versa.
- Degree of Accuracy Desired – If greater degree of accuracy is desired, the size of sample should be large. However, if samples are selected by an experienced person on the basis of scientific method, better results can be ensured, even in case of small size of sample.
- Homogeneity or Heterogeneity of the Population – In case, the population consists of homogeneous units, a small sample will serve the purpose. On the other hand, if the population consists of heterogeneous units, a large sample is required.
Requisites of a Good Sample (or Factors affecting Reliability of Sampling Data)
In order to reach at right conclusions, a sample must possess the following essential characteristics:
- Representative – Sample should be randomly selected so that each unit has equal chance of being selected. So, a trained and experienced person should select the sample. The aim is that selected sample should be representative of the characteristics of the population.
- Adequacy – To ensure that all the characteristics of a population are represented by the sample, its size must be adequate.
- Sampling Method – The method used to select the sample should be simple and exhaustive. Appropriate method ensures that the sample is representative and reduces sampling bias.
- No Personal Bias – If the sample is chosen in a biased way, the sampling results will not reflect the true characteristics of the overall population. So, the correspondents and Enumerators should not be biased.
Merits of Sampling Method
- Reduced Cost – It is more economical than the census technique as only a part of the population is studied.
- Greater Speed – Smaller volume of data saves time not only in collecting the information but also in the processing editing and analyzing the data.
- Reliable Results – With careful scientific sampling, well-trained investigators can provide more reliable results. Follow-up work can be undertaken much more effectively.
- Administrative Convenience – In case of sampling, scale of operation remains at low level. So, planning, organization and supervision can be conveniently managed, which leads to administrative conveniences.
Demerits of Sampling Method
- Difficult to achieve cent percent accuracy – As results are based on a sample, achieving a hundred percent degree of accuracy is not possible.
- Lack of Representativeness of the Sample – The accuracy of sampling method depends upon whether the sample is representative of the characteristics of the population. In practice, it is very difficult to obtain a sample which reflects all characteristics of the population.
- Bias in the selection of sample – If the investigator is biased, then he might select sample deliberately. In such cases, selected sample cannot be a representative of the characteristics of population.
Methods of Sampling (Types of Sampling)
- Random Sampling – It refers to a method in which every item in the universe has an equal chance of being chosen for the sample.
- The selection of sample items is independent of the person making the study.
- It is also known as ‘Probability Sampling’ because selection of sample works on Law of Probability as every item has a chance of being selected.
- Under this method, the sample is selected by the following two methods:
Lottery Method – In this method, all items of the population are numbered or named on separate slips of identical size. The slips are mixed in a bowl, and an unbiased person picks the slips blindly. Every item has an equal chance of being selected. For example – housing societies use lottery to allot parking spaces among residnets.
Random Number Tables – Random number table is simply a table of numbers generated by scrambling the digits 0, 1, 2 ……… 0 in a random manner. In this table, number are arranged in such a way that each number has an equal chance of being selected.
Merits of Random Sampling
- No personal Bias – Every item of the population has an equal chance of being selected. So, sample selection is free from personal bias of the investigator.
- Based on Probability – Every item has an equal chance of selection, so the rules of probability can be used to check accuracy and draw reliable conclusions about the population.
- Simple Method – It is very simple and easy to understand and apply.
Demerits of Random Sampling
- Not Suitable for small groups – This method may not give correct results if population is small.
- No Guarantee for Representative Sample – The sample might not be perfect representative of the population.
- Not Suitable for a Heterogeneous Population – If the population is very diverse, random sampling may not represent all groups proportionately, leading to bias in results.
2. Non – Random Sampling – Under non-random sampling method, the selection of a sample depends on the judgement and convenience of the investigator rather than on chance.
I. Judgement Sampling (or Purposive Sampling or Deliberate Sampling) – It is a method where the researcher intentionally selects certain units of the population on the basis of his own judgment and experience, considering them to be the most representative for the study.
Merits of Judgment Sampling
- Simple and easy – This method is simple and easy to adapt as it does not require complicated procedures to draw a sample.
- Proper Representation – This method enables the sample to be true representative of the population when the investigator has full knowledge of the composition of the universe and is free from bias.
- Avoid Irrelevant Items – This method helps to choose items in a sample which are of prime importance.
Demerits of Judgement Sampling
- Personal Prejudice – The personal prejudice or bias of the investigator may lead to a sample, which may not represent the population.
- Error of Judgement – The investigator may not know the whole population. So, there is a scope for the error of judgement in selection of the sample.
- Not an objective method – There is no scientific way to decide the sample size or sampling.
II. Quota Sampling – It is a method in which the population is divided into different groups or categories (like age, gender, income, etc.) and then a fixed number (quota) of samples is selected from each group. The selection within each group is done deliberately or conveniently by the investigator.
Merits of Quota Sampling
- Reliable Results – If the investigators are skilled and experienced, it gives more reliable and dependable results.
- Economical – The cost of preparing sample and field work is very law.
Demerits of Quota Sampling
- Personal Prejudice – There is considerable risk that a biased sample may be selected according to the personal prejudice of the investigator.
- Not possible to estimate Sample Error – It is not possible to estimate the sampling error and the degree of accuracy achieved.
III. Convenience Sampling – It is a method in which the investigator selects the sample that suits his convenience. This method is used when population of interest is very large or if investigation is to be completed in a short time-frame or the investigator does not have access to all the sub-groups. The main goal is to collect data quickly and with minimal effort.
Merits of Convenience Sampling
- Economical – It is less expensive and less time consuming.
- Easy Command – The units of the sample are easily located & contacted by the investigators.
- Suitable for Pilot Surveys – It is often used for making pilot studies in which questions are pre-tested and preliminary information is obtained before finalizing the sample design.
Demerits of Convenience Sampling
Merits of Convenience Sampling
- Economical – It is less expensive and less time consuming.
- Easy Command – The units of the sample are easily located & contacted by the investigators.
- Suitable for Pilot Surveys – It is often used for making pilot studies in which questions are pre-tested and preliminary information is obtained before finalizing the sample design.
Demerits of Convenience Sampling
- Lack of representation – The units of the sample selected under this method hardly represent the population.
- Personal Prejudice – Convenience samples are prone to bias by their nature.
- Unsatisfactory Results – The results obtained under this method are found to be unsatisfactory and misleading.
Statistical Errors – In Statistics, the work ‘Error’ is used in a specialized sense. Statistical Error refer to difference between the collected data and actual value of facts. In other words, it means the difference between actual or true value and estimated value. For example – if there are 500 workers employed in a factory and we count them as 495, then it will be a mistake. However, when all workers are gathered in a meeting and we approximate them as 503, then it will be called statistical error.
Types of Statistical Errors
- Sampling Errors – Sampling Error is the difference between the sample estimate and the actual value (or true value) of the whole population. It happens because we study only a part of the population, not the whole. For example – Suppose you have five students with an average height of 60 inches. If you take a sample of just two of them and their average height is 55 inches, then sampling error is 5 inches (the difference between the true value of 60 and sample’s estimate of 55). Sampling error can be reduced by taking a larger sample.
- Non-Sampling Errors – Non-sampling errors are errors that occur due to mistakes in the process of collecting, recording or processing of statistical data. It is difficult to minimize non-sampling error, even by taking a large sample. Even a Census can contain non-sampling errors.
Examples of Non-Sampling Errors
- Errors in Data Acquisition – this type of error arises from recording of incorrect responses or in recording the data. These errors occur due to mistakes by people involved in the survey, either the person asking the questions (the interviewer) or the person answering them (the respondent). For example – The actual weekly grocery spending of a family is Rs.1,200, but the respondent reports as Rs.1,500 or a student’s actual age is 14, but he reports it as 15.
- Non-Response Errors – Non- response occurs if an interviewer is unable to contact a person listed in the sample or a person from the sample refuses to respond. In this case, the sample observation may not be representative.
- Sampling Bias – It occurs when the sampling plan is such that.
Census Of India
The Census of India provides a complete demographic record of the population and is one of the largest administrative exercises undertaken in the world. It is being regularly conducted every 10 years since 1881; the first after independence was in 1951.
National Sample Survey Office
National Sample Survey Office (NSSO) was established in the year 1970 under the Government of India and it work under the Ministry of Statistics and Programme Implementation (MoSPI). Before that, it was known as National Sample Survey (NSS), which had started in 1950.
