Page 14 - Statistics for Dummies

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Statistics For Dummies, 2nd Edition
Getting with the Jargon ...............................................................................195
Interpreting Results with Confi dence .......................................................196
Zooming In on Width ...................................................................................197
Choosing a Confi dence Level .....................................................................198
Factoring In the Sample Size ......................................................................199
Counting On Population Variability ..........................................................201
Calculating a Confidence Interval for a Population Mean ......................201

Case 1: Population standard deviation is known ...........................202
Case 2: Population standard deviation
is unknown and/or n is small ........................................................203
Figuring Out What Sample Size You Need ................................................204
Determining the Confidence Interval for

One Population Proportion ....................................................................206
Creating a Confidence Interval for the Difference of Two Means ..........207

Case 1: Population standard deviations are known .......................208
Case 2: Population standard deviations are unknown
and/or sample sizes are small ......................................................210
Estimating the Difference of Two Proportions ........................................211
Spotting Misleading Confi dence Intervals ................................................213
Chapter 14: Claims, Tests, and Conclusions . . . . . . . . . . . . . . . . . . . . .215
Setting Up the Hypotheses .........................................................................216
Defining the null .................................................................................216

What’s the alternative? .....................................................................216
Gathering Good Evidence (Data) ...............................................................217
Compiling the Evidence: The Test Statistic .............................................218
Gathering sample statistics ..............................................................218
Measuring variability using standard errors ..................................218
Understanding standard scores .......................................................219
Calculating and interpreting the test statistic ...............................219
Weighing the Evidence and Making Decisions: p-Values ........................220
Connecting test statistics and p-values ..........................................220
Defi ning a p-value ...............................................................................221
Calculating a p-value ..........................................................................222
Making Conclusions ....................................................................................223
Setting boundaries for rejecting H .................................................224
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Testing varicose veins .......................................................................224
Assessing the Chance of a Wrong Decision .............................................225
Making a false alarm: Type-1 errors ................................................225
Missing out on a detection: Type-2 errors ......................................226
Chapter 15: Commonly Used Hypothesis Tests:
Formulas and Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227
Testing One Population Mean ....................................................................228
Handling Small Samples and Unknown
Standard Deviations: The t-Test .............................................................229
Putting the t-test to work ..................................................................230
Relating t to Z ......................................................................................231
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02_9780470911082-ftoc.indd xii 3/25/11 8:18 PM