Page 10 - Statistics II for Dummies

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Statistics II For Dummies
Chapter 2: Finding the Right Analysis for the Job . . . . . . . . . . . . . . . . .21

Categorical versus Quantitative Variables .................................................22
Statistics for Categorical Variables .............................................................23
Estimating a proportion ......................................................................23
Comparing proportions ......................................................................24
Looking for relationships between categorical variables...............25
Building models to make predictions ...............................................26
Statistics for Quantitative Variables ...........................................................27
Making estimates .................................................................................27
Making comparisons ...........................................................................28
Exploring relationships .......................................................................28
Predicting y using x .............................................................................30
Avoiding Bias .................................................................................................31
Measuring Precision with Margin of Error .................................................33
Knowing Your Limitations ............................................................................34

Chapter 3: Reviewing Confidence Intervals

and Hypothesis Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Estimating Parameters by Using Confi dence Intervals .............................38
Getting the basics: The general form of a confi dence interval ......38
Finding the confidence interval for a population mean ..................39

What changes the margin of error? ...................................................40
Interpreting a confi dence interval .....................................................43
What’s the Hype about Hypothesis Tests? ................................................44
What Ho and Ha really represent ......................................................44
Gathering your evidence into a test statistic ...................................45
Determining strength of evidence with a p-value ............................45
False alarms and missed opportunities: Type I and II errors.........46
The power of a hypothesis test .........................................................48

Part II: Using Different Types of Regression
to Make Predictions .................................................... 53

Chapter 4: Getting in Line with Simple Linear Regression. . . . . . . . . .55
Exploring Relationships with Scatterplots and Correlations ...................56
Using scatterplots to explore relationships .....................................57
Collating the information by using the correlation coeffi cient ......58
Building a Simple Linear Regression Model ...............................................60

Finding the best-fitting line to model your data...............................60
The y-intercept of the regression line ...............................................61
The slope of the regression line.........................................................62
Making point estimates by using the regression line ......................63

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