91Ó°ÊÓ

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

Direct Control and Blocking

Direct control refers to a situation in which the researcher eliminates any extraneous variable by keeping it constant during the experiment. Blocking, on the other hand, refers to when a researcher incorporates an extraneous variable into an experiment by creating different blocks for different levels of the variable and makes comparisons within these blocks.Blocking mostly intervenes when it concerns a variable that either can't be fixed or one that the researcher thinks might interact with the experimental manipulation.

02

Answer to Part a

The extraneous variable stature (height) was addressed by blocking. The researcher sorted the participants into three groups (blocks) based on their stature - 5th percentile, 50th percentile, and 95th percentile, and made comparisons within these blocks.

03

Answer to Part b

The potential effects of the extraneous variable, whether the right or left hand is used to operate the mouse, was dealt with by direct control. The researchers made sure all participants used their right hand in all stages of the experiment, thereby eliminating any influence this variable could have on the results.

Unlock Step-by-Step Solutions & Ace Your Exams!

• Full Textbook Solutions

  Get detailed explanations and key concepts

• Unlimited Al creation

  Al flashcards, explanations, exams and more...

• Ads-free access

  To over 500 millions flashcards

• Money-back guarantee

  We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

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

Direct Control

Direct control is a method used in experimental design to keep extraneous variables constant. This helps ensure that they do not influence the results of an experiment. In the context of the computer mouse study, direct control was crucial to maintaining consistency across participants. By ensuring that all subjects used their right hand to operate the mouse, researchers effectively removed handedness from affecting the outcome.
The aim was to isolate the impact of other factors, so any differences observed could only be attributed to the variable being investigated, and not the one controlled.

• Helps identify accurate cause-and-effect relationships.
• Improves the reliability of results.
• Reduces variability introduced by extraneous factors.

Blocking

Blocking is employed when a researcher aims to control extraneous variables by organizing subjects into different blocks based on these variables. Unlike direct control, which seeks to keep a variable constant, blocking acknowledges the variable but isolates its effect by creating groups.
In the computer mouse study, stature (height) was potentially an influential extraneous variable. Participants were grouped into blocks according to stature percentiles (5th, 50th, and 95th). This method allows researchers to conduct meaningful comparisons within blocks, ensuring any observed variations are not due to the blocked variable, but rather the primary variable of interest.

• Used when variables can't be kept constant.
• Results in more accurate comparisons.
• Can control for variability naturally present in samples.

Extraneous Variables

Extraneous variables are variables that are not of primary interest in a study but might affect the results. Identifying and addressing these variables is crucial to maintaining the integrity of the experiment's findings. If unaddressed, they can introduce confounding effects, making it difficult to determine the true relationship between the tested variables.
In this study, both stature and handedness are extraneous variables. Stature was managed by grouping participants into blocks, allowing researchers to analyze data without its interference. Handedness, on the other hand, was directly controlled by having everyone use the same hand, thus removing its potential influence altogether.

• Can hide the true effect of independent variables.
• Proper management improves the experiment's validity.
• Ignorance of such variables might lead to incorrect conclusions.