A single factor multi-level design is an experiment where one independent variable is manipulated to produce more than two distinct conditions. Researchers use this design when adding conditions can yield greater insights than a basic two-level comparison. For example, Darley and Latané's bystander experiment utilized this design by manipulating the independent variable to create three distinct conditions: a one witness condition, a two witnesses condition, and a five witnesses condition.

Single Factor Multi-Level Design

Which of the following correctly defines a single factor two-level design?

A single factor two-level design is an experiment that involves a single independent variable manipulated to create exactly two distinct conditions. For example, a researcher might investigate the effects of expressive writing by manipulating the independent variable to form two groups: a traumatic experience condition and a neutral experience condition.

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In an experiment, conditions refer to the distinct levels or variations of the independent variable that the researcher systematically creates through manipulation. Researchers typically assign these conditions short, descriptive names to make them easier to discuss. For example, a study investigating the effects of expressive writing on health might create a 'traumatic condition' and a 'neutral condition'.

Experimental Condition

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A between-subjects experiment is an experimental design approach wherein each participant is exposed to only a single level of the independent variable. This method differs fundamentally from within-subjects designs, as individuals are tested in just one specific condition rather than across all experimental variations.

Between-Subjects Experiment

It is important for researchers to distinguish between an independent variable and its conditions. A single independent variable represents the overarching factor being manipulated, while the conditions are the multiple different levels or variations created within that single variable.

Distinguishing Independent Variables from Conditions

A treatment condition is an experimental group in which participants actively receive the specific intervention or treatment being evaluated. To determine whether an intervention is effective, researchers compare the outcomes of participants in this condition against those assigned to a control condition.

Treatment Condition

A placebo is a simulated treatment that lacks any active ingredient or specific element intended to make it effective. Despite lacking active components, placebos are designed to mimic the appearance or experience of actual treatments, such as an identical-looking sugar pill in a drug trial or an unstructured conversation with a therapist in psychotherapy research.

Placebo

A control condition is an experimental baseline group in which participants do not receive the active treatment or intervention being tested. Researchers compare the outcomes of this untreated group to those in the treatment condition to ascertain if the intervention successfully produced a positive change.

Control Condition

In Darley and Latané’s bystander experiment, the independent variable was the perceived number of witnesses, which researchers manipulated to create three distinct conditions: participants believed there were either one, two, or five other students present. To maintain experimental control, the researchers held extraneous variables constant by testing everyone in the exact same room and exposing them to the identical simulated emergency. They also randomly assigned participants to these conditions to ensure the groups were similar from the start, effectively controlling for extraneous participant variables.

Example of Conditions and Control in Darley and Latané's Experiment

Single Factor Two-Level Design

In an experiment, researchers systematically create distinct levels or variations of a specific factor to study its effects. What is the term used for these distinct levels?

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