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(V) Do you use fertilizers in your field?


(I)  I live 10 meters away from the closest market.

(II) In this case, we need not ban, at the same time we should not encourage the use of plastic bags.

(II) No, I would also be opposed to increase in price of petrol by writing a request letter to the petroleum minister.

(IV) Yes, but it should be used when it is highly required.

(V) No, I use only manure.


You want to do research on the popularity of ‘vegetable atta noodles among children’. Design a suitable questionnaire for collecting this information:

(i) How do you like the flavour of this noodle?

(ii) How many times do you have this noodle for break-fast in a month?

(iii) What percentage of your income do you spend on atta noodles?

(iv) Is increase in noodles charges justified?

(v) How many times do you prefer to take noodles in your lunch box?


In a village of 200 forms, a study was conducted to find the cropping pattern. Out of 50 forms surveyed, 50% grew only wheat. Identify the population and the sample here:

In the population of 200 forms, 100 forms grew wheat.

In a sample of 50 forms, 25 forms grew wheat.


Give two examples each of population, sample and variable:

Example 1

Population: Total number of students in a school

Sample    : Number of students in class XI in that school

Variable   : Students


Example 2

Population: Total number of candidates in a join family

Sample    : Number of children in that family

Variable   : Each member in that member



(a) Census (b) Sample


Census or Complete Enumeration

A survey, which includes every element of the population, is known as Census or the Method of Complete Enumeration. . The essential feature of this method is that this covers every individual unit in the entire population. You cannot select some and leave out others.

This method would require huge expenditure, as a large number of enumerators have to be employed.



A sample refers to a group or section of the population from which information is to be obtained. A good sample (representative sample) is generally smaller than the population and is capable of providing reasonably accurate information about the population at a much lower cost and shorter time. Finally sampling method gives better result and is not expensive.


(a) Sampling error (b) Non-sampling error


Sampling error

The difference between the actual value of a parameter of the population (which is not known) and its estimate (from the sample) is the sampling error.

It is possible to reduce the magnitude of sampling error by taking a larger sample.

Non-sampling error

Non-sampling errors are more serious than sampling errors because a sampling error can be minimised by taking a larger sample. It is difficult to minimise non-sampling error, even by taking a large sample. Even a Census can contain non-sampling errors.

(i.e) Non-sampling error is more dangerous than sampling error.


Suppose there are 10 students in your class. You want to select three out of them. How many samples are possible?

There 10C3 = 120 samples are possible.


Does the lottery method always give you a random sample? Explain:

Yes, the lottery method always gives us a random sample. Because,It is an important and a simple method of selecting a random sample is to identify each element of a population by means of a card of a pack of uniform cards and to select required number of cards after a thorough mixing of cards(by a suitable machine).

The selection being made either with replacement (each card after drawing is replaced again in the pack) or without replacement.


Discuss how you would use the lottery method to select 3 students out of 10 in your class:

Assign each student with a card and a number. So there are 10 cards available. Mix them well with the help of a suitable machine.

Pick one card and the corresponding numbered student is selected. Similarly repeat the process and pick other two cards also.

Here, we cannot use with replacement lottery method; otherwise we may select the same card. By this way, we have to select three students out of 10 students.


Explain the procedure of selecting a random sample of 3 students out of 10 in your class by using the number table:

We can start using the table from anywhere, any page, column, row or point.

For the above quarry, we need to select a sample of 3 students out of 10 students in a class. A two digit number and therefore we consult two digit random numbers in sequence. We will skip the random numbers greater than 10. thus the 3 selected students are with serial numbers: 09, 03, 01.


What are the different sources of data?


Statistical data can be obtained from two sources.

The enumerator may collect the data by conducting an enquiry or an investigation.

Such data are called Primary Data, as they are based on first hand information.

If the data have been collected and processed (scrutinised and tabulated) by some other agency, they are called Secondary Data. Generally, the published data are secondary data.


Why do we do survey?


If a person wants to decide about a product, then he conduct a survey by asking questions about a particular product from a large group of people.

The purpose of surveys is to describe some characteristics like price, quality, usefulness (in case of the product) and popularity, honesty, loyalty (in case of the candidate).

The purpose of the survey is to collect data. Survey is a method of gathering information from individuals.



What do you mean by PILOT survey?

 Once the questionnaire is ready, it is advisable to conduct a try out with a small group which is known as Pilot Survey or Pre-Testing of the questionnaire.

The pilot survey helps in providing a preliminary idea about the survey. It helps in pre-testing of the questionnaire, so as to know the shortcomings and drawbacks of the questions.

Pilot survey also helps in assessing the suitability of questions, clarity of instructions, performance of enumerators and the cost and time involved in the actual survey.


What is the use of the term ‘survey’?


The first task in selecting a sample is to identify the population. Once the population is identified, the researcher selects a Representative Sample, as it is difficult to study the entire population.

 A sample refers to a group or section of the population from which information is to be obtained.

A good sample (representative sample) is generally smaller than the population and is capable of providing reasonably accurate information about the population at a much lower cost and shorter time.



What are the two main types of sampling? And define them


The two main types of sampling are Random and Non-random sampling.

As the name suggests, random sampling is one where the individual units from the population (samples) are selected at random.

In a non-random sampling method all the units of the population do not have an equal chance of being selected and convenience or judgement of the investigator plays an important role in selection of the sample.

They are mainly selected on the basis of judgment, purpose, convenience or quota and are non-random samples.


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