UNIT-I Introduction to Statistics PDF

UNIT-I INTRODUCTION TO STATISTICS: (Meaning) The word statistics is derived from the Latin word „Status‟ or Italian word „Statistika‟ or the German word „Statistik‟ which means a political state. The term statistics was applied to mean facts and f...

UNIT-I INTRODUCTION TO STATISTICS: (Meaning) The word statistics is derived from the Latin word „Status‟ or Italian word „Statistika‟ or the German word „Statistik‟ which means a political state. The term statistics was applied to mean facts and figures which were needed by the state in its day to day life. Statistics was regarded as a by-product of administrative activities of the State. Statistics is a tool in solving or analyzing the problem of the State. The word “statistics” is used in two different senses –Plural and Singular. When used as plural, statistics means numerical set of data and when used in singular sense, it means the science of statistical methods embodying the theory and techniques used for collecting, analyzing and drawing inferences from the numerical data. STATISTICS DEFINITION: “Statistics is the science which deals with the collection, classification, Presentation, analysis and interpretation of numerical data.” “Statistics may be called the science of counting”. - A. L. Bowley “Statistics may rightly be called the science of averages”. - A. L. Bowley “Statistics is the science of estimates and probabilities”. - Boddington CHARACTERISTICS OF STATISTICS: (Nature) ✓ Statistics are aggregate of facts. ✓ Statistics are affected to a marked extent by a multiplicity of causes. ✓ Statistics are numerically expressed. ✓ Statistics should be enumerated or estimated. ✓ Statistics should be collected with reasonable standard of accuracy. ✓ Statistics should be collected in a systematic manner for a pre-determined purpose. ✓ Statistics should be placed in relation to each other. 1  1. STATISTICS ARE AGGREGATE OF FACTS: Statistics deals with groups, but not individual items. For instance, one accident, one birth, one death, etc., cannot be called statistics. But the aggregate of figures relating to accidents, birth, death, etc., over different times or places can be called statistics. A single accident is not statistics. But the total number of accident of a city during a month is statistics. 2. STATISTICS ARE AFFECTED TO A MARKED EXTENT BY A MULTIPLICITY OF CAUSES: Quantitative data or statistical data are influenced by a number of factors. Social science- economics, history, sociology, etc., are affected by many factors. Statistics is most commonly used in social sciences. For instance, the fall in sales of a commodity is affected by a number of factors- supply, demand, market condition, general recession in trade, storage facility, currency, import, export, competition in market, consumer taste is not possible to single out one cause. 3. STATISTICS ARE NUMERICALLY EXPRESSED: Numerical data constitute statistics; students can be classified very good, good, average, and poor, etc., on the basis of their performance in tests. But they are in qualitative expressions and are not statistics. In particular, the qualitative characteristics- honesty, beauty, intelligence, etc., which cannot be measured numerically are not statistics. 4. STATISTICS SHOULD BE ENNUMERATED OR ESTIMATED: The numerical data pertaining to any field of enquiry can be obtained either by enumeration or by estimation. If the field of enquiry is not large, enumeration can be conducted. If the field of enquiry is wide and large, enumeration is not possible and in such cases, data can be estimated. 5. STATISTICS SHOULD BE COLLECTED WITH REASONABLE STANDARD OF ACCURACY: A reasonable standard of accuracy is needed in both enumeration and estimation. For instance, if the weights of students are being measured fractions of kilogram can be ignored; when measuring the distance from madras to kanyakumari fraction of a kilometer can easily be 2 ignored. No hard and fast rule can be laid down for all cases. Hence mathematical accuracy cannot be attained in statistical studies. 6. STATISTICS SHOULD BE COLLECTED IN A SYSYTEMATIC MANNER FOR A PRE-DETERMINED PURPOSE: The data should be collected in a systematic manner through some suitable plan. If not, there will be wastage of time energy and money. For instance, when we collected the income data from rich people, ignoring the poor, it will only inflate the national income data, the purpose of data collection must be decided in advance, and the investigator must be aware for the purpose. If the object is not known to the investigator, it is possible that he many collected unnecessary data, which many not be of any use while ignoring necessary data. Thus, without a pre-determined purpose, the collected data may not yield the desired results. 7. STATISTICS SHOULD BE PLACED IN RELATION TO EACH OTHER: Statistical data are mostly collected for the purpose of comparison. In order to make valid comparison the data should be homogeneous, i.e., they should relate to the same phenomenon or subject. For instance, weights of the boys in a class are to be compared with the corresponding weights of boys in another class. But it would be meaningless to compare the height of the student with the height of trees. Scope of statistics: (I) statistical and industry: Statistical methods and statistical data are very useful for an industry. They play the most complementary role. Statistical methods help in the maintenance of records of inventory, purchase, production and marketing. They also help to do the difficult task of deciding when and where to purchase the raw materials, how to schedule the production, how to exploit the market and how best to utilise the available men, machinery and capital. (II) Commerce and Business: Statistics can facilitate decision-making and performance reviews for a business. From statistics, the business can understand how customers behave and react to its offerings, the 3 business can also understand how the business itself is performing and make improvements to the processes. Market survey gives the demand condition and also the likely changes. Buying and selling can be adjusted accordingly. (III) Statistics and Mathematics : Statistics are related advancement in statistical technique, that are outcome from mathematics. (IV) Economic All Economic plans of a formulated on the basis of statistical data. The success of the plan is also evaluated with the help of statistics. Economic problems such as production, consumption, wages, price profits, unemployment, poverty, etc. can be expressed numerically 4