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# Chp_3 - CHAPTER 3 Data Description Introduction Statistical...

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8/3/10 CHAPTER 3 Data Description

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Click to edit Master subtitle style 8/3/10 Introduction Statistical methods can be used to summarise data. 8 Measures of average are also called measures of central tendency and include the mean, median, mode, and midrange. Measures that determine the spread of data values are called measures of variation or measures of dispersion and include the range, variance, and standard
8/3/10 Introduction (cont’d.) Measures of position tell where a specific data value falls within the data set or its relative position in comparison with other data values. 8 The most common measures of position are percentiles, deciles, and quartiles. The measures of central tendency, variation, and position are part of what is called traditional statistics. This type of data is typically used to confirm conjectures about the data. 8 Another type of statistics is called exploratory data analysis. These techniques include the the box plot and the five-number summary. They can be used to explore data to see what they show.

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8/3/10 Basic Vocabulary A statistic is a characteristic or measure obtained by using the data values from a sample. 8 A parameter is a characteristic or measure obtained by using all the data values for a specific population.
8/3/10 An example We have said that statisticians use samples taken from populations; however, when populations are small, it is not necessary to use samples since the entire population can be used to gain information. For example, suppose an insurance manager wanted to know the average weekly sales of all the company’s representatives. If the company employed a large number of salespeople, say nationwide, he would have to use a sample and make an inference to the entire sales force. But if the company had only a few people, say only 87 agents, he would be able to use all people’s sales for a randomly chosen week and thus use the entire population. In this case, the average of the sales from a sample of representatives is a

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Click to edit Master subtitle style 8/3/10 Measure of Central Tendency A measure of central tendency is a value used to represent the typical or “average” value in a data set. Measures of central tendency are also called Measures of average and include the mean, median, mode, and midrange.
Click to edit Master subtitle style 8/3/10 Mean (The Arithmetic Average) Mean is the sum of all data values divided by the number of values in the data set. The mean of a sample data set is denoted by ( x bar) and the mean of a population data set by the μ (Greek letter mu). x Obj101 N x = μ where n represents the total number of values in where N represents the total number of values in the

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Click to edit Master subtitle style 8/3/10 An Example Q1- This data represents the statistic quiz score (out of 10) for each of the 7 students. Find the mean of the following data set: 8 9 98 7 9 6
8/3/10 Things to Note Convention: In statistics, Greek letter are used to denote parameters, and Roman letters are used to denote statistics.

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Chp_3 - CHAPTER 3 Data Description Introduction Statistical...

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