Page 15 - Statistics for Dummies

Table of Contents
Handling negative t-values ................................................................231
Examining the not-equal-to alternative ...........................................232
Testing One Population Proportion ..........................................................232
Comparing Two (Independent) Population Averages ............................234
Testing for an Average Difference (The Paired t-Test) ............................236
Comparing Two Population Proportions .................................................240
Part V: Statistical Studies and the Hunt
for a Meaningful Relationship ................................... 243
Chapter 16: Polls, Polls, and More Polls . . . . . . . . . . . . . . . . . . . . . . . .245
Recognizing the Impact of Polls .................................................................245
Getting to the source .........................................................................246
Surveying what’s hot .........................................................................248
Impacting lives ...................................................................................248
Behind the Scenes: The Ins and Outs of Surveys ....................................250 xiii
Planning and designing a survey .....................................................250
Selecting the sample ..........................................................................254
Carrying out a survey ........................................................................256
Interpreting results and fi nding problems......................................259
Chapter 17: Experiments: Medical Breakthroughs
or Misleading Results? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .261
Boiling Down the Basics of Studies ...........................................................262
Looking at the lingo of studies .........................................................262
Observing observational studies .....................................................263
Examining experiments .....................................................................264
Designing a Good Experiment ....................................................................264
Designing the experiment to make comparisons ..........................265
Selecting the sample size ..................................................................267
Choosing the subjects .......................................................................268
Making random assignments ............................................................269
Controlling for confounding variables ............................................270
Respecting ethical issues ..................................................................272
Collecting good data ..........................................................................273
Analyzing the data properly .............................................................274
Making appropriate conclusions .....................................................275
Making Informed Decisions ........................................................................277
Chapter 18: Looking for Links: Correlation and Regression. . . . . . . .279
Picturing a Relationship with a Scatterplot .............................................280
Making a scatterplot ..........................................................................281
Interpreting a scatterplot..................................................................281
Quantifying Linear Relationships Using the Correlation ........................282
Calculating the correlation ...............................................................283
Interpreting the correlation ..............................................................284
Examining properties of the correlation .........................................286

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