Copyright © 2003–2008 by Stan Brown, Oak Road Systems
Cuing: start 11 min in and play 8½ minutes.
________________________ studies are usually more reliable than single-sample investigations. One type is a _______________ _____________________ study, where pairs are matched up. A random member of each pair gets the _________________, and the __________________ between the two results in the pair is your data. Another kind is the classic ______________ and _____________ study on the ___________ ________________.
Example: Loss of ___________________
over time
Taste of cola is evaluated right after it’s made, and again after
one month. The difference will be analyzed with a _________ ____
test.
Panelists are first ___________________ by reference to fixed points on the ____________________ scale. Then they taste their samples and record their data. A month later they come back and do it again, with aged cola. This eliminates all sources of _______________________ besides the _______________ in the cola itself. Ha is that sweetness after one month is ______________ initial sweetness. It’s a __________-tailed test because researchers are only interested in whether cola ____________ sweetness over time.
Sweetness ratings are shown below left. We first found the _____________________ between the pairs of scores. This last column is a _____________ ___________ of observations to analyze.
| Panelist | Before | After | d = B−A |
|---|---|---|---|
| 1 | 6.3 | 4.3 | 2.0 |
| 2 | 7.8 | 7.4 | 0.4 |
| 3 | 7.7 | 7.0 | 0.7 |
| 4 | 6.7 | 4.7 | 2.0 |
| 5 | 7.8 | 8.2 | -0.4 |
| 6 | 8.1 | 5.9 | 2.2 |
| 7 | 9.3 | 10.6 | -1.3 |
| 8 | 7.9 | 6.7 | 1.2 |
| 9 | 6.2 | 5.1 | 1.1 |
| 10 | 8.2 | 5.9 | 2.3 |
x̄ = _________, meaning that the mean taste score
_______________ by 1 unit over a month’s time.
s = ________.
Ho: μd ______ 0 (sweetness doesn’t deteriorate)
Ha: μd ______ 0 (sweetness deteriorates over time)
df = ______, p (from table) is between _____ and _____.
(From TI-83, p = .0104.)
_____________ Ho and ______________ Ha. Conclusion: Sweetness of the test soda __________ over time.
Three advantages of t tests:
1. Don’t need to know _________
2. __________ samples are okay
3. Test is ___________ (works fairly well for non-____________
distribution, if n > about _______)
Caution:
Must have a good __________ sample, and watch out for
___________.
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