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Experimental Designs: Post-test Only. Jordan DeWitt March 12, 2008. Classical Experiment Process. 1. Subjects are randomly assigned to an experimental or control group so that no systematic difference exists between the two groups.
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Experimental Designs: Post-test Only Jordan DeWitt March 12, 2008
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.
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.
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.
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
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
The Daily Show Effect Candidate Evaluations, Efficacy, and American Youth
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.
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.
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.
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.
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.
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.
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)
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)
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)
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.
