In the advertiser example where 80 percent of women noticed brighter skin after using a cleanser for a month, why does this statistic mean 'little to nothing'?
Explanation
This question uses the advertiser example from the text to reinforce the main limitation of the one-group posttest only design: without a comparison, the results are uninterpretable.
Other questions
In a one-group posttest only design, how is the study conducted?
What is identified as the major limitation of the one-group posttest only design?
How is a one-group pretest-posttest design described in comparison to a within-subjects experiment?
If an anti-drug program airs on television between the pretest and posttest of a study on student attitudes toward drugs, this exemplifies which threat to internal validity?
The threat to internal validity known as 'maturation' occurs when participants change between the pretest and posttest due to what?
What is 'regression to the mean' in the context of a pretest-posttest design?
According to the text, a bowler with a long-term average of 150 who suddenly bowls a 220 will almost certainly do what in the next game, due to regression to the mean?
The tendency for many medical and psychological problems to improve over time without any treatment is known as what?
In their review of depression studies, what did Posternak and Miller find about the improvement of participants in waitlist control conditions?
What is the primary feature of an interrupted time-series design that distinguishes it from a one-group pretest-posttest design?
In Hans Eysenck's classic 1952 article summarizing psychotherapy studies, what proportion of patients were found to have improved between the pretest and posttest?
What was Eysenck's main conclusion after comparing the improvement rate in psychotherapy patients to archival data from state hospitals?
The 1980 book by Mary Lee Smith, Gene Glass, and Thomas Miller, which summarized hundreds of experiments on psychotherapy, found that overall psychotherapy was what?
When a researcher selects participants for a study because of their extremely low scores on a variable, and their scores are higher on a subsequent test, what threat to internal validity is most likely at play?
What is the primary advantage of an interrupted time-series design as illustrated in the hypothetical study on student absences?
The threat of 'instrumentation' to internal validity refers to a situation where...
When does the 'testing' threat to internal validity occur in a pretest-posttest design?
Why must one be cautious about inferring causality from pretest-posttest designs?
What type of quasi-experimental design is described as the weakest?
A one-group pretest-posttest design is unlike a true within-subjects experiment because...
Which threat to internal validity is concerned with naturally occurring changes in the participants themselves over time, such as growing older or becoming more experienced?
If human observers used to measure behavior become fatigued or change their standards over time during a study, this is an example of which threat to internal validity?
What did Eysenck (1952) use as a comparison for his finding that two-thirds of psychotherapy patients improved?
In the classic interrupted time-series design example from Cook and Campbell (1979), what was the treatment that was found to increase productivity?
What is the common approach mentioned in the text to rule out threats to internal validity such as history and maturation when using a one-group design?
In a one-group pretest-posttest study of a year-long anti-drug program, participants becoming better reasoners over the year could be responsible for a change in attitudes. This is an example of what threat?
What problem does regression to the mean pose when participants are selected for a study because of their extreme scores?
In the hypothetical interrupted time-series graph (Figure 8.1) where the treatment for absences 'did not work', what did the data show?
What was the conclusion of the 1980 meta-analysis by Smith, Glass, and Miller regarding psychotherapy?
A researcher measures attitudes, completes a treatment, and then measures attitudes again. What design is this?
The common cold improving over a week, regardless of whether someone eats chicken soup, is used as an example of what concept?
In a one-group posttest only study, a researcher implements an anti-drug program and then measures students' attitudes. Why is it difficult to determine the program's effectiveness?
When a change in a dependent variable in a pretest-posttest design could be due to participants having further thoughts inspired by the pretest itself, this is which threat to internal validity?
What challenge from Hans Eysenck did the hundreds of experiments conducted by 1980, summarized by Smith, Glass, and Miller, take up?
An interrupted time-series design involves a set of measurements taken at intervals over a period of time that is 'interrupted' by what?
Why would adding a control group to a one-group pretest-posttest design be beneficial?
What did the meta-analysis by Smith, Glass, and Miller (1980) find about the improvement of psychotherapy participants compared to control participants?
A researcher notices that participants became bored with the attitude measure at posttest and were less careful in their responses compared to the pretest. This is an example of which threat to validity?
One-group designs are a type of which broader category of research?
In Eysenck's 1952 article, he concluded that there was no evidence that psychotherapy was effective. What was his recommendation based on this conclusion?
If a researcher wants to measure productivity each week for a year and introduces a new work policy midway through, what is the most appropriate design described in this chapter?
A one-group pretest-posttest design is susceptible to which of the following threats to internal validity?
When comparing the two hypothetical line graphs of student absences in Figure 8.1, the key difference that indicates an effective versus an ineffective treatment is the...
Which of the following describes a 'history' threat to internal validity?
If you are studying the effectiveness of a new teaching method on a class of students by giving a test before and after the method is implemented, and a student in the class wins a national academic award during that time, this event could be considered what kind of threat?
The text states that in a one-group pretest-posttest design, 'if the average posttest score is better than the average pretest score... then it makes sense to conclude that the treatment might be responsible'. Why is this conclusion not certain?
What is the key difference between the one-group posttest only design and the one-group pretest-posttest design?
According to the text, a one-group pretest-posttest design is much like a within-subjects experiment in that each participant is tested first under a control condition and then a treatment condition. What serves as the 'control condition' in this design?
The fact that results from one-group posttest only designs are 'frequently reported in the media and are often misinterpreted by the general population' suggests what about the design?