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The report "Comparative Study of Two Computer Mouse Designs" (Cornell Human Factors Laboratory Technical Report RP7992) included the following description of the subjects used in an experiment: Twenty-four Cornell University students and staff ( 12 males and 12 females) volunteered to participate in the study. Three groups of 4 men and 4 women were selected by their stature to represent the 5 th percentile (female \(152.1 \pm 0.3 \mathrm{~cm},\) male \(164.1 \pm 0.4 \mathrm{~cm}), 50\) th percentile (female \(162.4 \pm 0.1 \mathrm{~cm},\) male \(174.1 \pm 0.7 \mathrm{~cm}),\) and 95 th percentile (female \(171.9 \pm 0.2 \mathrm{~cm},\) male \(185.7 \pm 0.6 \mathrm{~cm}\) ranges \(\ldots\) All subjects reported using their right hand to operate a computer mouse. This experimental design incorporated direct control and blocking. a. Are the potential effects of the extraneous variable stature (height) addressed by blocking or direct control? b. Whether the right or left hand is used to operate the mouse was considered to be an extraneous variable. Are the potential effects of this variable addressed by blocking or direct control?

Step by step solution

01

Analyzing effect of stature

At the beginning, consider how the researchers addressed stature in their experiment. They selected participants based on their stature and created three different groups: 5th percentile, 50th percentile, and 95th percentile. Each group contained individuals of similar stature. This is an example of blocking. In spaning the range of statures, the experimenters can more legitimately claim their findings apply to most anyone.

02

Analyzing effect of hand usage

Next, consider how the researchers addressed the hand used to operate the mouse. All participants reported using their right hand to operate a computer mouse. This factor was held constant throughout the entire experiment, meaning the researchers applied direct control to this variable. By doing this, they can ensure variations in the signal are due to the actual variable being tested (the mouse design) rather than whether participants used their right or left hand.

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Key Concepts

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

Blocking in Experiments

In experimental design, blocking is a technique that aims to reduce variability in the experimental results by grouping subjects based on certain characteristics. This helps ensure that the results are more reliable and applicable across different subsets of participants.
For instance, in the mouse design study, researchers grouped subjects by their stature. By creating groups that represent different stature percentiles, they effectively used blocking to manage the potential variations that could arise from differences in height.
This is particularly useful when the characteristic, such as height, might influence the outcome. Blocking allows researchers to separate out this influence, embracing a more focused examination of the primary variables of interest. Essentially, blocking helps in gaining clearer insights by minimizing variability arising from extraneous factors.

Direct Control in Experiments

Direct control in experiments involves holding certain variables constant to eliminate their potential impact on the outcome. This method is used when a particular variable is identified, but its variation is unnecessary for the objectives of the study.
In the described mouse design experiment, direct control is evident in the choice to use only participants who are right-handed. By ensuring all subjects use the same hand, researchers effectively control this variable. This control enhances the study's validity, as it confirms that any observed differences are due to the design of the mouse, not the variations in hand usage.
Utilizing direct control, researchers ensure that the experimental conditions remain consistent. This consistency significantly contributes to maintaining the integrity and focus of the study, ensuring the findings meaningfully reflect the effects of the main variable under investigation.

Extraneous Variables

Extraneous variables are factors other than the independent variable that might affect the dependent variable in an experiment. Their presence can confound the results, muddling the interpretation and reliability of the findings.
In the exercise, stature and handedness were identified as extraneous variables. While stature was managed through blocking, handedness was controlled directly. By doing this, the researchers minimized the potential impact of these variables on the outcome of the study.
It's crucial for experimenters to recognize and address extraneous variables so they do not skew results. Effective handling of these variables ensures a purer examination of the primary factors in the study. Whether through blocking or direct control, managing extraneous variables strengthens the overall experimental design by enhancing clarity and reducing unintended impact on the results.