An agent's preferences are said to be strongly monotonic if, given a consumption bundle , the agent prefers all consumption bundles that have more of at least one good, and not less in any other good.

Direct personal investigation: The investigator, in this case, makes personal observation of the subject of enquiry and does so with his own discretionary powers to undertake work according to his own choice. The data collected through Direct Personal Interview is original, real, pure and without use. This method can be used when area of enquiry is limited or when a maximum degree of accuracy is needed. Thus, this method ensures high degree of accuracy of investigation.

Some recent definitions have been called growth definitions.

1. According to Professor Henry Smith, "Economics is the study of how in a civilized society one obtains the share of what other people have produced and of how the total product of society changes and is determined."
2. According to Jacob Viner, "Economics is what economists do."
3. According to Paul A Samuelson, "Economics is the study of how men and society choose, with or without the use of money, to employ scarce productive resources which could have alternative uses, to produce various commodities over time and distribute them for consumption now and in future amongst various people and groups of society."

Importance of statistics:

1. Formulation of economic laws: it helps in formulation of laws and models e.g. law of demand  has been developed by the inductive method of genralisation which is based on statistical principles.
2. Understanding economic problems: it plays a  vital role in understanding and solving economic problems such as poverty, unemployment, etc.
3. Study of market structures: study of monopoly, monopolistic competition, oligopoly, and monopolistic competition requires statistical comparison of market prices, cost, and profits of individual firms.
4. Intersectoral anf intertemporal  comparison:  statistics helps in the comparision of different sectors of the economy and also helps in comparison of variables in two different time periods
5. Economic forcasting: by using statistical tools , methods, and techniques one can forcast e.g growth of the country in the coming  fiscal year or rate of inflation in the coming month. 

Consumers's budget refers to the total amount of money that the consumer can afford to spend on consumption of different goods and services given his/her limited income. 

Statistics is indispensable to almost all sciences - social, physical and natural. It is very often used in most of the spheres of human activity. In spite of the wide scope of the subject it has certain limitations. Some important limitations of statistics are the following:

1. Statistics does not study qualitative phenomena: Statistics deals with facts and figures. So, the quality aspect of a variable or the subjective phenomenon falls out of the scope of statistics. For example, qualities like beauty, honesty, intelligence etc. cannot be numerically expressed. So, these characteristics cannot be examined statistically. This limits the scope of the subject.
2. Statistical laws are not exact: Statistical laws are not as exact as in case of natural sciences. These laws are true only on average. They hold good under certain conditions. They cannot be universally applied. So, statistics has less practical utility.
3. Statistics does not study individuals: Statistics deals with aggregate of facts. Single or isolated figures are not statistics. This is considered to be a major handicap of statistics.
4. Statistics can be misused: Statistics is mostly a tool of analysis. Statistical techniques are used to analyze and interpret the collected information in an enquiry. As it is, statistics does not prove or disprove anything. It is just a means to an end. Statements supported by statistics are more appealing and are commonly believed. For this, statistics is often misused. Statistical methods rightly used are beneficial but if misused these become harmful. Statistical methods used by less expert hands will lead to inaccurate results. Here the fault does not lie with the subject of statistics but with the person who makes wrong use of it.
5. Uniformity and homogeneity of data: Statistics can deal with only homogeneous and uniform data. Heterogeneous data are not comparable and hence statistical tools can't be applied on them. It does not make sense to compare weight of human beings with weight of cows or buffaloes. Sometimes data are available in different units and are collected under different circumstances. It also makes their comparison illogical.
6. Only Experts can make proper use of Statistics: Statistics can be properly used only by experts. A layman can't derive right meaning from statistical statements. According to King, "The science of statistics is most useful servant but only of great value to those who understand its proper use.

Classification of economic sectors on the basis of economic of activities are as follows :

(i) Primary sector : When we produce goods by exploiting natural resources, it is an activity of the primary sector, such as agriculture, dairy farming, fishing, forestry.

 (ii) Secondary sector: In this, natural products are changed into other forms through manufacturing that we associate with industrial activity. The product is not produced by nature but has to be made and therefore, some process of manufacturing is essential. For example, using cotton fibre from the plant we spin, yarn and weave cloth.

(iii) Tertiary sector : It helps in the development of the primary and secondary sectors. They provide aid or a support for the production process. Transport, storage, communication, banking, trade are some examples of tertiary activities.

Some of  the reasons for the above remark  "there are three lies-lie, damn lie and statistics",may be enumerated as follows :

1. Figures are innocent and believable, and the facts based on them are psychologically more convincing. But it is a pity that figures do not have the label of quality on their face. 
2. Arguments are put forward to establish certain results which are not true by making use of  inaccurate figures or by using incomplete data, thus distorting the truth. 
3. Though accurate, the figures might be moulded  and manipulated by dishonest and unscrupulous persons to conceal the truth and present a working and distorted picture of the facts to the public for personal and selfish motives.

Hence, if Statistics and its tools are misused, the fault does not lie with the science of Statistics. Rather, it is the people who misuse it, are to be blamed.

Demand is defined as the quantity of a commodity that a consumer is willing and able to purchase m the market in a given period of time and at each possible price.
E.g. a consumer demands 5 kg of sugar m a month at a price of Rs 40 per kg.

A questionnaire is a list of questions relating to the field of enquiry. A questionnaire can be either a mailed questionnaire or a questionnaire filled by an enumerator.  It is an instrument of collecting primary data from a large number of people. Mailed questionnaires are sent to the respondents along with a covering letter whereas the enumerator fills the questionnaire personally by visiting the respondents.