Page 15 - Intermediate Statistics for Dummies

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Intermediate Statistics For Dummies
Chapter 2: Sorting through Statistical Techniques . . . . . . . . . . . . . . . .31
Qualitative versus Quantitative Variables in Statistical Analysis ............32
Statistics for Qualitative Variables...............................................................33
Comparing proportions.......................................................................33
Estimating a proportion ......................................................................34
Looking for relationships between qualitative variables................34
Building models to make predictions................................................36
Statistics for Quantitative Variables ............................................................37
Making comparisons............................................................................37
Finding connections.............................................................................38
Making predictions...............................................................................40
Avoiding Bias ..................................................................................................41
Looking at bias through statistical glasses.......................................41
Settling the variance controversy: The battle of n–1 versus n.......42
Getting Good Precision..................................................................................44
Understanding precision from a statistical point of view...............44
Measuring precision with margin of error ........................................45
Making Conclusions and Knowing Your Limitations.................................47
Chapter 3: Building Confidence and Testing Models . . . . . . . . . . . . . .49
Estimating Parameters By Using Confidence Intervals.............................50
Getting the basics: The general form of a confidence interval ......50
Finding the confidence interval for a population mean ..................51
What changes the margin of error?....................................................53
Interpreting a confidence interval......................................................56
Setting Up and Testing Models.....................................................................57
What do Ho and Ha represent — really? ...........................................57
Gathering your evidence into a test statistic....................................58
Determining strength of evidence with a p-value ............................59
Deconstructing Type I and Type II errors .........................................60
Getting empowered by the power of a hypothesis test ..................62
Part II: Making Predictions by Using Regression ...........67
Chapter 4: Getting in Line with Simple Linear Regression . . . . . . . . .69
Exploring Relationships with Scatterplots and Correlations ...................70
Using scatterplots to explore relationships......................................71
Collating the information by using the correlation coefficient ......72
Building a Simple Linear Regression Model ...............................................73
Finding the best-fitting line to model your data...............................74
The y-intercept of the regression line................................................75
The slope of the regression line .........................................................76
Making estimates by using the regression line.................................76