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Never leave home without duct tape There have been anecdotal reports of the ability of duct tape to remove warts. In an experiment conducted at the Madigan Army Medical Center in the state of Washington ( Archives of Pediatric and Adolescent Medicine \(2002 ; 156: 971-974)\), 51 patients between the ages of 3 and 22 were randomly assigned to receive either duct-tape therapy (covering the wart with a piece of duct tape) or cryotherapy (freezing a wart by applying a quick, narrow blast of liquid nitrogen). After two months, the percentage successfully treated was \(85 \%\) in the duct tape group and \(60 \%\) in the cryotherapy group. a. Identify the response variable, the explanatory variable, the experimental units, and the treatments. b. Describe the steps of how you could randomize in assigning the 51 patients to the treatment groups.

Step by step solution

01

Identify the Response Variable

The response variable is the outcome of the treatment on the patients. In this experiment, it is the effectiveness of the treatment, measured by the percentage of patients whose warts have been successfully treated after two months.

02

Identify the Explanatory Variable

The explanatory variable is the treatment method applied to the patients. In this experiment, it categorizes the patients into two groups: those receiving duct-tape therapy and those receiving cryotherapy.

03

Identify the Experimental Units

The experimental units are the individual patients participating in the study. In this case, there are 51 patients who are the subjects of the experiment.

04

Identify the Treatments

The treatments are the specific procedures or interventions applied to the experimental units. Here, the treatments are duct-tape therapy and cryotherapy.

05

Randomize Assignment to Treatment Groups

To randomize the assignment of 51 patients to two treatment groups, you could use random numbers or a coin flip for each patient. Alternatively, you could number the patients from 1 to 51 and use a random number generator to assign patients to either the duct tape group or the cryotherapy group, ensuring each group is roughly equal in size.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Response Variable

In the field of experimental design, the response variable is a crucial element as it represents the outcome that the experiment seeks to measure. In this particular study, the response variable is the effectiveness of the treatment in successfully removing warts. After two months of treatment, researchers measured success by the percentage of patients who showed no signs of warts. This variable is what the research is ultimately trying to influence or predict.
Understanding the response variable helps in knowing what the research aims to prove or disprove. A higher percentage of treated patients with no warts indicates greater treatment success. Therefore, tracking this variable provides the necessary data for evaluating the experiment's efficacy.

Explanatory Variable

The explanatory variable in an experiment is a factor that might cause changes to the response variable, essentially the independent variable being manipulated by the researchers. In this wart removal study, the explanatory variable is the type of treatment applied—either duct-tape therapy or cryotherapy.
By categorizing the subjects into these two distinct treatment groups, researchers assess how different methods influence the outcome. The explanatory variable thus provides a means to compare the effectiveness of each treatment method against the observed response variable.

Randomization

Randomization is a fundamental principle in experimental design that ensures each participant has an equal chance of being assigned to any treatment group. This method helps to eliminate bias and confounding variables that could skew the results.
For the wart removal study, randomization involved assigning the 51 patients randomly to either the duct tape or cryotherapy group. Techniques such as using a random number generator or simple coin flips are common practices. These methods help ensure that each group is representative of the population, making the experiment more reliable and the results more generalizable. Randomization is vital for creating comparable groups, allowing researchers to conclude that observed differences in outcomes are due to treatments rather than other factors.

Treatments

In an experimental context, treatments refer to the specific interventions administered to the experimental units. Here, the treatments are duct-tape therapy and cryotherapy, each applied to a separate group of patients.
Each treatment aims to achieve the same goal—removal of warts—but through different methodologies. Duct-tape therapy involves covering the wart with duct tape, while cryotherapy involves freezing the wart with liquid nitrogen. Comparing the effects of these treatments on the response variable (wart removal effectiveness) allows researchers to determine which method is more efficient.

• Duct-tape therapy: covering the wart.
• Cryotherapy: freezing the wart.

Understanding the nature and application of these treatments is essential for analyzing the experiment’s results and drawing valid conclusions on their effectiveness.