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Experimental Designs: Post-test Only

Experimental Designs: Post-test Only

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Experimental Designs: Post-test Only

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  1. Experimental Designs: Post-test Only Jordan DeWitt March 12, 2008

  2. Classical Experiment Process • 1. Subjects are randomly assigned to an experimental or control group so that no systematic difference exists between the two groups. • 2. A pretest, measuring the dependent variable, is administered to both groups • 3. The experimental group is exposed to the treatment; the control group is not. • 4. A post-test, again measuring the dependent variable, is administered to both groups. • 5. The amount of change in the dependent variable between the pretest and post-test is determined for each group.

  3. Post-test Only Process • 1. Subjects are randomly assigned to an experimental or control group so that no systematic difference exists between the two groups. • 2. A pretest, measuring the dependent variable, is administered to both groups • 3. The experimental group is exposed to the treatment; the control group is not. • 4. A post-test, again measuring the dependent variable, is administered to both groups. • 5. The amount of change in the dependent variable between the pretest and post-test is determined for each group.

  4. Definition • An experimental design identical to that of the classical experiment except for the absence of a pretest. This assumes that the pretest is expendable due to random assignment of subjects.

  5. Advantages • Reduces costs • Reduces hassle • Useful for large study populations • Prevents against “single-group threats” to internal validity • History Threat • Maturation Threat • Testing Threat • Instrumentation Threat • Mortality Threat • Regression Threat

  6. Disadvantages • If done incorrectly, internal validity is high. • Only for use in large, randomly-assigned groups • Not useful if the extent of change is needed to be determined

  7. The Daily Show Effect Candidate Evaluations, Efficacy, and American Youth

  8. Introduction • Soft news, defined- news programs featuring lower levels of public affairs information and focus more on drama, sensationalism, human interest themes, and personalities. • Examples: Dr. Phil, Oprah, The Tonight Show (Leno), The Late Show (Letterman) and The Daily Show with Jon Stewart.

  9. Past Research • Baum (2002) argues that soft news creates a more knowledgeable citizenry by educating an inattentive public that would not otherwise follow “hard” news. • Most existing research focuses on the effects of candidate’s appearance on a soft news program. Little study has been done on the effects of a candidate’s appearance when he/she is not present. • Recent research has suggested that high levels of cynicism and distrust detract from democratic discourse and overall public interaction.

  10. The Daily Show with Jon Stewart • Styled as a fake news program and regularly pokes fun at mainstream news-makers. • Growing in popularity • Things to remember about its viewers • They are young. • They are relying less on mainstream political news sources. • The majority of viewers report learning at least some news from watching it, even though it not intended to be a legitimate news source.

  11. Hypotheses • 1. Young viewers’ evaluations of presidential candidates will become more negative with exposure to campaign coverage on The Daily Show. • 2. Young viewers’ evaluations of John Kerry will be more negative than those of George W. Bush with exposure to campaign coverage on The Daily Show.

  12. Hypotheses • 3. Young viewers’ cynicism toward the electoral system will increase with exposure to campaign coverage on The Daily Show. • 4. Young viewers’ cynicism toward the news media will increase with exposure to campaign coverage on The Daily Show.

  13. Experiment Design • Post-test only controlled experiment • 732 randomly-selected college freshmen selected from political science courses • 3 Groups • The 1st group viewed a video clip (8 minutes long) of selected 2004 election coverage from The Daily Show. • The 2nd group view a video clip (same amount of time and similar coverage topics) from the CBS Evening News. • The 3rd group was the control group. They saw no news coverage and were given the same test.

  14. Findings • The evaluation variable for Bush and Kerry was an additive index of several survey items, rated 1-5. • Evaluations for Bush and Kerry are negatively associated with exposure to The Daily Show. When Bush’s index is combined with Kerry’s, there is a significant negative effect, when compared to the second group (hypothesis 1 is valid)

  15. Findings • It is also seen that, the lesser established candidate’s, Kerry’s, index is more negatively affected by exposure to The Daily Show than the incumbent’s. (hypothesis 2 is valid) • The Daily Show caused a 23% increase in the probability that a participant would disagree that he or she has faith in the electoral system. No such relationship existed for those who watched the CBS News. (hypothesis 3 is valid)

  16. Findings • Holding all other variables in the model constant, those who did not see TheDaily Show clip had a .48 probability of disagreeing with a statement that “I trust the news media to cover political events fairly and accurately.” Those who did see the clip had a .59 probability of disagreeing. (hypothesis 4 is valid)

  17. Strengths/Weakness of this Design • Lack of real-world applicability • The effects of the stimuli may be short-lived. • Results uncovered in a post-test survey tend to wash out after a short duration of time.

  18. Questions?