What type of research allows a researcher to control a variable?
Research Designs are platforms to use to explore new knowledge in order to better understand phenomena, clarify explanations and identify causative factors. Although there are no real rules for choosing a design; one must realize the consequences for choosing one design over the other. One should choose the design that best attempts to address the conceptual issues presented. Show Some questions that would help you decide which quantitative design is most appropriate for your study include:
The purpose of an experimental design is to provide a structure for evaluating the cause-and-effect relationship between a set of independent and dependent variables. Some of the elements of an experimental design:
True experimental design: including random selection (random sampling), pretest/posttest, random assignment, manipulation of the levels of the independent variable(s), including a control group. Posttest-only design: (after-only design): you must assume that randomization assures pre-experimental group equivalence. Solomon four-group design: combines the true experimental and the posttest only. Allows you to evaluate the effect of the pretest on the posttest scores, and any interaction betwen the test and experimental condition. Factorial designs: Allows the researcher to examine the effects of one or more intervention on different factors or levels of variables in the study. Used for statistical control. Tends to increase sample size because you want to have enough subjects in each "cell" of the design. Counterbalanced (crossover) designs: when more than one intervention (treatment) is used, and you want to know the effect of manipulating the order in which the treatments are given. DePoy gives three criteria that need to be met to determine that a true experimental design is appropriate:
QUASI EXPERIMENTAL DESIGNS It is not always possible to implement a design that meets the three criteria of a true experimental study (manipulation, control and randomization). Quasi-experimental designs differ from experimental designs because either there is no control group or randomization cannot occur. Types of quasi experimental designs: 1. Nonequivalent control group design:
Pretest-posttest design: no randomization, not much control. Like a one-shot case study with a pretest. Static group comparison: still no randomization, but maybe a little more control. You have a "control group", but those subjects are non-equivalent, and there is no pretest to see how equivalent they might have been.NONEXPERIMENTAL DESIGNS These designs are used in situations where manipulation of an independent variable, control or randomization are not involved. These designs are focused to describe and measure independent and dependent variables. They are sometimes called descriptive research designs. Nonexperimental research does not prove causality. The goal is to describe phenomena and explore and explain relationships between variables. What type of research has a control variable?Control variables in experiments
In an experiment, a researcher is interested in understanding the effect of an independent variable on a dependent variable. Control variables help you ensure that your results are solely caused by your experimental manipulation.
What type of research allows the researcher to control and manipulate the variables?Experimental research allows the researcher to control the situation. In so doing, it allows researchers to answer the question, “What causes something to occur?” Permits the researcher to identify cause and effect relationships between variables and to distinguish placebo effects from treatment effects.
What does it mean for a researcher to control for a variable?In causal models, controlling for a variable means binning data according to measured values of the variable. This is typically done so that the variable can no longer act as a confounder in, for example, an observational study or experiment.
In which type of research study would the researcher use a control group?In a scientific study, a control group is used to establish causality by isolating the effect of an independent variable. Here, researchers change the independent variable in the treatment group and keep it constant in the control group. Then they compare the results of these groups.
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