Enjoy learning Statistics Online! Please be sure to share and subscribe to our YouTube channel.


Course Documents

Chapter 1 - Intro

Chapter 2 - Methods for Describing Sets of Data

Chapter 3 - Probability

Chapter 4 - Discrete Random Variables

Chapter 5 - Normal Random Variables

Chapter 6 - Sampling Distributions

Chapter 7 - Confidence Intervals

Chapter 8 - Tests of Hypothesis: One Sample

Chapter 9 - Confidence Intervals and Hypothesis Tests: Two Samples

Sample Exam I: Chapters 1 & 2

Sample Exam II: Chapters 3 & 4

Sample Exam III: Chapters 5 & 6

Sample Exam IV: Chapters 7 & 8

Problem 1

8.5 Small-Sample Test of Hypothesis about a Population Mean

The CEO of Equifax credit reporting agency claims the average credit rating has dropped below 675 points.  A study of 20 randomly selected credit scores had an average of 660 points and a standard deviation of 95.3 points.  Use a 5% significance level to test the claim that credit scores are now on average below 675 points.  The CEO claims the results are not valid since they came from too small a sample.  Is there any merit to his argument?  

« back