Chapter 3 Notes - Variance: Population Variance: What are...

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MGMT 305 Business Statistics Chapter-3 What is Statistics? In everyday usage, statistics refers to numerical facts. In a broad sense, statistics is the art and science of collecting, analyzing, presenting, and interpreting data. Population vs. Sample: Population: The set of all elements of interest in a particular study. Sample: A subset of the population. Descriptive statistics: Descriptive statistics are the tabular, graphical, and numerical methods used to summarize data. Three Numerical Descriptive Statistics: Mean, Variance, Standard deviation
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Mean: The average of all data. Let x 1 , x 2 , . .., x n be the members of a sample and the mean of the sample (sample mean ) be: Let x 1 , x 2 , . .., x N be the members of a population and the mean of the population (population mean) be: Variance: Variance is the average of the squared differences between each data value and the mean. Sample
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Unformatted text preview: Variance: Population Variance: What are and ? Standard Deviation: The standard deviation is the positive square root of the variance. It has the same units as the data, which makes it more easily comparable to the mean than the variance. Sample Standard Deviation: Population Standard Deviation: NOTATIONS: Population Sample Mean Variance 2 s 2 Standard Deviation s Why Mean, Variance, and SD? Which Supplier would you choose? Supplier A Supplier B Mean Of delivery Times 8 10 SD of delivery times 3.5 3 Example: Police records show the following numbers of daily crime reports for a sample of days during the summer months Summer 28 18 24 32 18 a. Compute the mean and Sample variance ( both formulas) b. Compute the standard deviation Summer x i 1 75 2 78 3 79 4 77 5 75 6 73 7 75 8 77 Sum Average...
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This note was uploaded on 12/06/2011 for the course MGMT 305 taught by Professor Priya during the Fall '08 term at Purdue University-West Lafayette.

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Chapter 3 Notes - Variance: Population Variance: What are...

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