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Chapter One
An Introduction to Business Statistics
McGraw-Hill/Irwin Copyright © 2004 by The McGraw-Hill Companies, Inc. All rights reserved.
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An Introduction to Business Statistics
1.1 Populations and Samples
1.2 Sampling a Population of Existing Units
1.3 Sampling a Process
1.4 Ratio, Interval, Ordinal, and Nominative Scales of Measurement
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Populations and Samples
Population
A set of existing units (people, objects, or events)
Variable
A measurable characteristic of the population
Quantitative (real-valued)/Quantitative (real-valued)/Qualitative (categorical)Qualitative (categorical)
Census
An examination of the entire population of measurements
Sample
A selected subset of the units of a population
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Populations and Samples
Population
Sample
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Descriptive Statistics and Statistical Inference
Descriptive Statistics
The science of describing important aspects of a set of measurements
Statistical Inference
The science of using a sample of measurements to make generalizations about important aspects of a population
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Sampling a Population of Existing Units
Random Sampling
A procedure for selecting a subset of the population units in such a way that every unit in the population has an equal chance of selection
Sampling with replacement
When a unit is selected as part of the sample, its value is recorded and placed back into the population for possible reselection
Sampling without replacement
Units are not placed back into the population after selection
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Approximate Random Samples
Frame
A list of all population units. Required for random sampling, but not for approximate random sampling methods like systematic and voluntary response sampling.
Systematic Sample
Every k-th element of the population is selected for the sample
Voluntary Response Sample
Sample units are self-selected (as in radio/TV surveys)
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Process
A sequence of operations that takes inputs (labor, raw materials, methods, machines, and so on) and turns them into outputs (products, services, and the like.)
ProcessInputs Outputs
Sampling a Process
A process is in statistical control if it displays constant level and constant variation.
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Runs Plot
A runs plot is a graph of individual process measurements over time.
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Runs Plot – Payment Time Example
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Scales of Measurement
RatioQuantitative scale, ratios are meaningful, inherently defined zero. (e.g. salary, height, distance.)
IntervalQuantitative scale, but ratios not meaningful nor is there an inherently defined zero. (e.g. temperature)
OrdinalQualitative or categorical scale with meaningful ordering or ranking of categories. (e.g. income classification)
NominativeQualitative scale without meaningful ordering among categories (e.g. gender, ethnic classification)
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An Introduction to Business Statistics
1.1 Populations and Samples
1.2 Sampling a Population of Existing Units
1.3 Sampling a Process
1.4 Ratio, Interval, Ordinal, and Nominative Scales of Measurement
Summary: