lec1.2 - 1 Lecture 1 CHAPTER 1 SAMPLING AND DESCRIPTIVE...

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1 Lecture 1: CHAPTER 1: SAMPLING AND DESCRIPTIVE STATISTICS Question: What is a statistic? Answer: Any numerical summary measure based on data from a sample; contrasts with a parameter which is based on data from a population. Basic Idea of Statistics The basic Idea behind all statistical methods of data analysis is to make inferences about a population by studying a relatively small sample chosen from it. Sampling (Section 1.1, page 3) STATISTICS deals with the of DATA. Data may arise naturally as observations of “things as they are”, or as a result of a controlled designed experiment. As mentioned, statistical methods are based on the idea of analyzing a sample drawn from a population . For this to work, the collection of data must be done carefully and according to certain rules. We will explore one of these methods, called SIMPLE RANDOM SAMPLING . The
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2 important thing to keep in mind is that data collected incorrectly may invalidate any conclusion we may draw from it. For example : Let’s say we wish to test the heights of students at UOIT by measuring a sample of 100 students. How should we choose the 100 students to measure? Some methods are obviously bad: Thus, a simple random sample is ideal. Once your data is collected, it is often useful to describe the data through displays or summaries that bring attention to certain characteristics which may be of interest to us. The techniques used for such descriptions will involve us in the area of DESCRIPTIVE STATISTICS, which we will explore later today. Definition: a population is the set of all measurements or objects of interest in a particular study. Example: I want to test the average alcohol consumption in all adults (19 and over) residing in Oshawa. What would my population be? Question: If the population is the thing that interests an investigator, why doesn’t he/she just simply examine each member in the population. Answer:
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3 Thus to obtain information about the population the investigator must use a __________. Definition: a sample is a subset of the population. Definition: a simple random sample (srs) is a sample chosen in such a way that each member of the population has an equal chance of being chosen. Reason for using a srs?
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This note was uploaded on 06/20/2011 for the course STAT 2800 taught by Professor Paula during the Winter '11 term at UOIT.

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lec1.2 - 1 Lecture 1 CHAPTER 1 SAMPLING AND DESCRIPTIVE...

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