University of Phoenix Material
Week 4 Practice Worksheet
Prepare a written response to the following questions.
Chapters 9 &11
1. Two boats, the Prada (Italy) and the Oracle (USA), are competing for a spot in the upcoming America’s Cup race. They race over a part of the course several times. The sample times in minutes for the Prada were: 12.9, 12.5, 11.0, 13.3, 11.2, 11.4, 11.6, 12.3, 14.2, and 11.3. The sample times in minutes for the Oracle were: 14.1, 14.1, 14.2, 17.4, 15.8, 16.7, 16.1, 13.3, 13.4, 13.6, 10.8, and 19.0. For data analysis, the appropriate test is the t-Test: Two-Sample Assuming Unequal Variances.
The next table shows the results of this independent t-test. At the .05 significance level, can we conclude that there is a difference in their mean times? Explain these results to a person who knows about the t test for a single sample but is unfamiliar with the t test for independent means.
We can conclude that there is a significant difference in the mean times. To find cut-off, I used df=16, alpha level=0.5. Using the t-table, I found the cutoff point 2.12 and then used t-value -3.76.
If a person doesn’t undertand t-test for independent means, we can take as example an IQ test whereby our group showed that the single sample has significant difference in mean values in comparison with total population. It means failure of the null hypothesis and that our alternative hypothesis is true.
Hypothesis Test: Independent Groups (t-test, unequal variance)
difference (Prada - Oracle)
standard error of difference
confidence interval 95.% lower