I started by informing the class that the exams were still not completely marked because a few students entered their student numbers incorrectly on the scan sheets. This was taking us some time to sort out and that the results would be available early Week 10. However, a random sample of n = 5 exams which were marked manually revealed a sample mean of 79%, with a 95% CI ranging from 70% to 88%.
I then returned to the confidence interval problem for a proportion and talked about the election polls where interviewing roughly 1000 respondents is sufficient to get a 95% CI with a 3.1% margin of error. We found the correct sample size from a formula for n. This completed the discussion of Chapter 7.
Chapter 8 started with a taste test where a student claimed that he/she can tell the difference between Coke and Pepsi. The null hypothesis was that he/she would just be guessing. See this link for details of the experiment.
Null and alternative hypotheses were discussed in greater detail which were followed by a definition and examples of Type I and Type II errors. A one-sided test example with z-test involving cigarette tar content was presented. I then talked about the very important matter of p-value and showed that this value was very small in the cigarette example resulting in rejecting H0 for all α > p. The class ended with an example involving the DSB GMAT scores for 2005 (where the p value was very large, given the sample mean).
2 comments:
Just wondering if we might be getting out exams back soon?
This is now the only class where we have not received our marks.
Please post the marks as soon as possible.
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