Giffen goods are special kind of goods on which the consumers spends most of his income and their demand rises with an inrease in price and demand falls with decrease in price level. For example when the prices of jowar, bajra reduces, then the consumer tends to consumer less of those items and consume superiror goods such as wheat and rice.

Complementary goods: meaning of complementary is ‘useful or attractive together’. These are the goods which used together. Increase/ decrease in demand for one good will increase/decrease demand for other good also.

Ex: car and petrol, mobiles and mobile covers etc

Substitute goods: substitute goods have inverse relationship to each other i.e Increase in price of one good will decrease the consumption of that particular good and demand for another good increases.

Ex: increase in price of coffee makes people to have tea instead of coffee.

Normal goods: Normal goods refer to those goods that share a positive relationship with income. That is, as the income increases, the demand for normal goods increases. On the other hand, as the income falls, the demand for normal goods falls. For example, clothing is a normal good. As income increases, the demand for clothing increases, and as income falls the demand for clothing falls.

Inferior goods: Inferior goods refer to those goods that share an inverse relationship with income. That is, as against normal goods, as the income increases, the demand for inferior goods falls and vice-versa. For example, coarse cereals are inferior goods. As the income increases, the consumer reduces its demand for coarse cereals and instead shifts its demand towards superior quality cereals. On the other hand, as the income falls, the consumer increases the demand for coarse cereals.

The word statistics is used both in plural as well as in singular sense. In plural sense, statistics means numeric facts which can be used to draw conclusions and in singular sense, it means the statistical methods with the help of which statistical information is used to treat and draw conclusions from them.
There are following limitations of statistics :
Sometimes, when data are not properly collected 1 then there is likelihood to draw wrong conclusions.
Therefore, it is necessary to know the limitations of statistics.
(i) Statistics does not study about individuals : Statistics are expressed in facts. It does not study individuals. For example, there are five students in a class. Statistics only tells the average marks obtained in class not how many marks are obtained by every student in the class.
(ii) It does not study the qualitative aspect of problem : The most important condition of statistical study is that subject of investigation and inquiry should be capable of being qualitatively measured. For example, honesty, poverty, etc.
(iii) Statistics can be misused: The result obtained can be manipulated accordingly to one’s own interest and such manipulated results can mislead the community.
(iv) Statistical results lack mathematical accuracy: The results drawn from statistical analysis are normally in approximates. As the satistical analysis is based on observation of mass data, number of inaccuracies may be present and it is difficult to rectify them.
(v) Uniformity and homogeneity of data : It is essential that data must have the quality of uniformity and homogeneity. Heterogeneous data are not comparable. For example, it would be meaningless to compare the heights of men with heights of trees because these figures are of heterogeneous character.

share market is a place where shares of pubic listed companies are traded. The primary market is where companies float shares to the general public in an initial public offering (IPO) to raise capital.

PPC is concave to the origin because of increasing Marginal opportunity cost. This is because inorder to increase the production of one good by 1 unit more and more units of the other good have to be sacrificed since the resources are limited and are not equally efficient in the production of both the goods. 

Law of demand states that there is an  inverse relationship between the price and quantity demanded of a commodity, keeping other factors constant i.e., price of substitutes goods, taste of the consumer, income of the consumer etc.