w2-intro1-print

# w2-intro1-print - Descriptive Statistics and Inferential...

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Descriptive Statistics and Inferential Statistics Example Descriptive Statistics is the procedure of putting the observations into tabular form and drawing the corresponding histogram. Inferential Statistics helps us to answer the following questions: What is the error of using the sample mean to estimate the population mean? How to reduce such error? If the sample mean is 5.5 feet, could we claim this is strong evidence that the population mean is less than 6 feet? How to quantify the possible errors above?

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Population and Sample Population is the set of measurements of interest in a statistical study. Sample is a subset of measurements selected from the population of interest. Our primary interest is the population. We infer the characteristics in the population on the basis of information from a sample.
Parameters and Statistics Parameters numerical descriptive measures computed from population measurements Statistics numerical measures computed from sample measurements Under a fixed population, parameters are constant though they may be unknown. Statistics corresponding to the same measurement change from sample to sample and so they are random (involving uncertainty).

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Types of Data / Variable Categorical Data (Qualitative Data) Nominal Data No natural order between the categories e.g. Do you have a personal computer? Yes or No Ordinal Data Order exists e.g. What is the Standard & Poor „s Rating of your bank? Numerical Data (Quantitative Data) Discrete Data The values are distinct & separate. e.g. How many magazines do you currently subscribe? Continuous Data Infinite number of possible values. e.g. How tall are you ?
Pie and Bar Charts Fortune magazine publishes a list of the world‟s billionaires each year. The 1992 list include 233 individuals. Their wealth, age and geographic location (Asia, Europe, Middle East, United States, and Other) are reported.

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Pie and Bar Charts The exact count and the average wealth can be presented via bar chart.
Pie and Bar Charts Key features of pie charts: First used by Florence Nightingale (Famous nurse, after the war between England and Russia in Crimea around 1856) to point out ”the major cause of deaths in the Army was not wounds caused by enemy action but disease caused by lack of proper sanitation.” (http://elvis.rowan.edu/ kilroy/JEK/05/18.html) For categorical data only.

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## This note was uploaded on 01/01/2010 for the course ISOM ISOM111 taught by Professor Anthonychan during the Spring '09 term at HKUST.

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w2-intro1-print - Descriptive Statistics and Inferential...

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