EBP Chapter 10- Experimental Research: One-Way Designs

overview of experimental research

IV is manipulated by arranging different experiences for research participants and then assess impact

overview of non-experimental research (observational)

does not give treatment, interventions, or provide an exposure (do not control/manipulate variables)

Hierarchy of Evidence

differences affect placement on the hierarchy of evidence

what does the hierarchy of evidence compare?

causality versus risk

which type of research in the hierarchy of evidence is the "gold standard?"

randomized controlled trials (RCTs)

what is an experimental research design used for?

to demonstrate cause and effect rather than happening by chance:

-control or manipulate variables

-use randomized controlled trial or controlled clinical trial

-random assignment of participants to groups = decreased biases

characteristics of a One-Way experimental design

-has 1 independent variable

-the independent variable is created (manipulated)

-levels (experimental conditions)- refers to the specific situations that are created within the manipulation

what are the two levels (experimental conditions) of one-way research designs?

-experimental condition

-control condition

define experimental condition

level of the IV in which the situation of interest is created

define control condition

level of the IV in which the situation was not created

EX: Children who viewed violent cartoons would play more aggressively than those who had viewed nonviolent cartoons.

What is the independent variable?

type of cartoon

EX: Children who viewed violent cartoons would play more aggressively than those who had viewed nonviolent cartoons.

What are the levels of the IV?

violent v. nonviolent cartoons

EX: Children who viewed violent cartoons would play more aggressively than those who had viewed nonviolent cartoons.

What is the dependent variable?

aggressiveness of play

what is a between-subjects design?

-every participant experiences only one condition and...

-researchers assess group differences between participants in various conditions

what is a within-subjects design?

-each participant experiences all conditions and...

=researchers test the same participants repeatedly for differences between conditions

what is a one-way between participants experimental design?

a one-way experimental design with two levels of the independent variable

within subjects design

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another name for Quasi-Experimental research

nonrandomized research design

quasi-experimental research is similar to experiments in...

design (manipulating tx) and purpose

participants in quasi-experimental research

participants are not randomized, which leads to group equivalency being uncertain

characteristics of Analysis of Variance (ANOVA)

-very similar to t-test

-compares the means of the dependent variable across the levels of an experimental research design (3+ levels)

-different types (1-way and 2-way ANOVAS)

if the experimental manipulation has influenced the dependent variable...

there will be significantly more variability among the means of the group

how is the F statistic is calculated?

calculated as the ratio of the two variances

-compare the p-value to alpha to make a decision

ANOVA summary table

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disadvantages of experiments (4)

-some variables cannot be manipulated (eg. race, family background, intelligence, etc) -- correlational designs

-lab situations/artificial environments may influence participants behavior

-oversimplification of reality

-ethical dilemmas