Page 13 - Statistics for Dummies

Table of Contents
Chapter 10: The t-Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
Basics of the t-Distribution .........................................................................157
Comparing the t- and Z-distributions ..............................................157
Discovering the effect of variability on t-distributions .................159
Using the t-Table ..........................................................................................159
Finding probabilities with the t-table ..............................................160
Figuring percentiles for the t-distribution ......................................160
Picking out t*-values for confi dence intervals ...............................161
Studying Behavior Using the t-Table .........................................................162
Chapter 11: Sampling Distributions
and the Central Limit Theorem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .163
Defining a Sampling Distribution ...............................................................163

The Mean of a Sampling Distribution ........................................................164
Measuring Standard Error ..........................................................................166
Sample size and standard error .......................................................166
Population standard deviation and standard error ......................168 xi
Looking at the Shape of a Sampling Distribution ....................................169
Case 1: The distribution of X is normal ...........................................170
Case 2: The distribution of X is not normal —
enter the Central Limit Theorem .................................................170
Finding Probabilities for the Sample Mean ..............................................173
The Sampling Distribution of the Sample Proportion .............................175
Finding Probabilities for the Sample Proportion .....................................177
Part IV: Guesstimating and Hypothesizing
with Confidence ....................................................... 179
Chapter 12: Leaving Room for a Margin of Error. . . . . . . . . . . . . . . . . .181
Seeing the Importance of That Plus or Minus ..........................................181
Finding the Margin of Error: A General Formula .....................................183
Measuring sample variability ...........................................................183
Calculating margin of error for a sample proportion ....................184
Reporting results ...............................................................................186
Calculating margin of error for a sample mean .............................187

Being confident you’re right .............................................................188
Determining the Impact of Sample Size ....................................................189
Sample size and margin of error ......................................................189
Bigger isn’t always (that much) better!...........................................189
Keeping margin of error in perspective ..........................................190

Chapter 13: Confidence Intervals:
Making Your Best Guesstimate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193
Not All Estimates Are Created Equal .........................................................193
Linking a Statistic to a Parameter ..............................................................194

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