NCERT Solution for Class 11 Commerce Statistics for Economics Chapter 2  Collection of Data
NCERT Solution for Class 11 Commerce Statistics for Economics Chapter 2  Collection of Data Page/Excercise 20
 Which of the following is the most important when you buy a new dress?
a. Dress quality
b. Brand
c. Price
d. Colour
 How often do you use a computer?
a. 02 hours/day
b. 24 hours/day
c. 46 hours/day
d. 68 hours/day
 Which of the following newspaper/s do you read regularly?
a. The Times of India
b. The Hindustan times
c. Indian Express
d. The Hindu
 Rise in the price of petrol is justified.
a. As demand for petrol is rising
b. As petrol has no close substitutes
c. As price of crude oil is rising in the international market
d. As petrol duty has increased
 What is the monthly income of your family?
a. Rs 0Rs 20,000
b. Rs 20,000Rs 40,000
c. Rs 40,000Rs 60,000
d. Rs 60,000 and more
NCERT Solution for Class 11 Commerce Statistics for Economics Chapter 2  Collection of Data Page/Excercise 21
 Do you like Economics?
 Do you study daily?
 Will you be visiting your hometown during the summer vacations?
 Are you satisfied with your Class X marks?
 Do you do your homework daily?
 There are many sources of data. False.
There are not many but only two sources of data which are primary and secondary sources of data. A primary source of data is firsthand data which is collected by a researcher from the original source, whereas secondary data is collected by someone in the past and is used by the researcher.
 Telephone survey is the most suitable method of collecting data when the population is literate and spread over a large area. False.
A telephone survey is most suitable when the population is illiterate and spread over a large area. Under this method, questions are asked from the respondents over the phone, and thus, respondents need not read the questions given in the questionnaire.
 Data collected by an investigator is called secondary data. False.
Data collected by an investigator is called primary data and not secondary data. Secondary data is collected by someone in the past and is used by the researcher.
 There is a certain bias involved in the nonrandom selection of samples. True.
In the nonrandom selection of items, every item does not have an equal chance of getting selected in the sample. Thus, there are chances of personal biases in the nonrandom selection of samples.
 Nonsampling errors can be minimised by taking large samples. False.
Nonsampling errors cannot be minimised by taking large samples. In fact, nonsampling errors increase by taking large samples. This is because such errors are related to collection of data such as measurement error, nonresponse error and calculation error.
 This question is an openended question. Various responses can be received from different individuals. Thus, it will become difficult for the investigator to deal with such kind of varied information. The question can be asked in the following way:
What is the distance between your house and the closest market?
a. 02 km
b. 24 km
c. 46 km
d. More than 6 km
 This question is not clear in the sense that it does not give a clear idea to respondents about how to answer it. The question should be framed in the following manner:
Should the use of plastic bags be banned?
a. Yes
b. No
 This question has double negatives which might confuse respondents. Also, such a question may lead to majority of responses against the petrol price rise. The correct way of asking this question is
Is the increase in the price of petrol justified?
a. Yes
b. No
 The given questions are not asked in the correct order. First, general questions should be asked followed by specific ones. The correct order of questions is
a. What is the yield per hectare in your field?
b. Do you use fertilisers in your field?
c. Do you agree with the use of chemical fertilisers?
QUESTIONNAIRE on Popularity of Vegetable Atta Noodles
1. Name: ______________________ 2. Age: ____________ 3. Address: ______________________________ 4. Class: IV _____ VIX ______ XIXII _____ 5. Sex: Male _______ Female ________ 6. Do you like noodles? Yes _____ No______ 7. Do you like Vegetable Atta Noodles? Yes _____ No______ 8. How many times do you consume Vegetable Atta Noodles in a week? 01 ___________ 12 ____________ 23 ____________ 34 ____________ 9. Are you satisfied with the flavours present in Vegetable Atta Noodles? Yes _____ No______ 10. Do your parents eat noodles with you? Yes _____ No______ 11. Do you have any suggestions for Vegetable Atta Noodles? ________________________________________________________________________

Population is the total items studied under an investigation. Thus, here, population is 200 farms. On the contrary, a sample is a group of items taken from the population to make a conclusion about the population. Out of the population, i.e. 200 farms, 50 farms were surveyed. Hence, the sample is 50 farms.
Example 1: 30 students were selected from the Commerce XII batch of 120 students to know the average marks obtained by Commerce students.
Sample: 30 students
Population: 120 students
Variable: Marks
Example 2: A study was conducted to know the income level of 1800 families living in ABC Housing Society. For this, data was collected from 200 families.
Sample: 200 families
Population: 1800 families
Variable: Income
The sample method gives better results as compared to the census method because
 Less costly: The sample method is less costly as only some items of the population are studied rather than all the items of the population.
 Time saving: This method saves a lot of time and energy of the investigator as fewer items of the population are studied.
 Easy identification of errors: Errors under the sampling method can be easily identified and rectified as the number of items is small.
 Feasible for large population: When the size of the population is large, the sampling method is feasible as the cost of conducting the census becomes high.
 Less nonsampling errors: The number of nonsampling errors in the sampling method is less because a limited number of items are studied.
A nonsampling error is more serious than a sampling error as a nonsampling error cannot be minimised by taking a larger sample size. A nonsampling error arises because of errors in the collection of data such as measurement error, nonresponse error, misinterpretation by respondents and calculation error. On the other hand, a sampling error can be minimised by taking a larger sample size as the sampling error arises because of a small sample size.
Using the lottery method to select 3 students out of 10 in the class:
 Make ten paper slips of equal size and write the name of each student on each slip.
 Put all the slips in a box and mix them.
 Draw three slips at random without replacement.
 Students whose names are written on the slips are selected.
Yes, the lottery method always gives a random sample. Because just like a random sample, in the lottery method, every unit of population has an equal chance of being selected.
3 students are to be selected out of 10 students. Here, 10 is the largest number of students; thus, we would use a twodigit random number in sequence. Thus, the selected students would be 5^{th}, 3^{rd} and 9^{th} after skipping the random number greater than 10.
Samples provide better results than surveys as
 Less costly: The sample method is less costly as only some items of the population are studied.
 Time saving: This method saves a lot of time and energy of the investigator as fewer items of the population are studied.
 Easy identification of errors: Errors under the sampling method can be easily identified and rectified as the number of items is small.
 Feasible for large population: When the size of the population is large, the sampling method is feasible as the cost of conducting it is low.
 Less nonsampling errors: The number of nonsampling errors in the sampling method is less as a limited number of items are studied.