# 712 key words mean median and mode 64 lesson 8

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7.12. KEY WORDS Mean, Median and Mode.

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64 LESSON 8 SAMPLING DISTRIBUTION AND ESTIMATION 8.1. INTRODUCTION Human welfare including daily actions of human beings leans heavily on statistics. Inferring valid conclusions for making decision needs the study of statistics and application of statistical methods almost in every field of human activity. Statistics, therefore, is regarded as the Science of Decision - making. The statisticians can commonly categories the techniques of statistics which are of so diverse into (a) descriptive statistics and (b) inferential statistics (or inductive statistics). The former describes the characteristics of numerical data while the latter describes the judgment based on the statistical analysis. In other words, the former is process of analysis. In other words, the former is process of analysis whereas the latter is that of scientific device of inferring conclusions. Both he are systematic methods of drawing satisfactory valid conclusions about the totality i.e. (population) on the bias of examining a part of population, termed as sample. The process of studying the sample and then generalizing the results to the population needs a scientific investigation searching for truth. 8.2. OBJECTIVES The main aim of this Lesson is to study the Basics of sampling. After going through this Lesson you should be able to understand 1. Population 2. Sample 3. Sampling technique 4. Probability sampling 5. Non probability sampling 8.3. CONTENTS 8.3.1. Population and sample 8.3.2. Parameter and statistics 8.3.3. Sampling techniques 8.3.4. Probability sampling 8.3.5. Non probability sampling 8.3.6. Sample and distribution 8.3.7. Estimation theory 8.3.8. Illustration 8.3.1. POPULATION AND SAMPLE The word population is technical term in statistics, not necessarily referring to people. It is totality of objects under consideration. In other words, it refers to a number of objects or items which are to be selected for investigation. This term as sometimes called the universe. Figure 1 shows the concept of population and a sample in the form of the Venn diagram where population is shown as the universal set and a sample is shown as a true subject of the population.
65 Population Sample Fig 1 A population containing a finite number of objects say the students in a college, is called finite population. A population having an infinite number of objects say, heights or weights or ages of people in the country, starts in the sky etc. is known as an infinite population. Having concrete objects say, the number of books in a library, the number of bases or scooters in a district, etc. is called existent population. If the population consists of imaginary objects say, throw of die or coin in infinite numbers of times is referred to hypothetical population.

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• Spring '12
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