Variables and its types

1. Topic:
Variables
Prepared by: Nadia Sarwar

2. Contents:
– Variable
– Independent Variables
– Levels of Independent Variables
– Active and Assigned Variables
– Dependent Variables Intervening Variables
– Confounding and Extraneous Variables
– Functional Relationships
– References

3. Variables and its types:
– Variables are aspects that change over the course of research, whether clinical
or not, as well as clinical practice itself.
– Understanding their nature and function is critical, certainly for clinical practice,
and, in research, particularly for experimentation.
–Types of Variable:
They are broadly designated as independent and dependent variables, with the
former presumed to be causes and the latter presumed to be effects of those
causes.

4. Independent Variable:
– Independent variables are aspects of a study that a scientist-practitioner either
controls or chooses.
– They are independent because they do not rely on other variables
– for their changes.
– They are causes of outcomes, or at least presumed causes of outcomes.
Example: Treatment

5. Levels of Independent Variable:
– Any independent variable must have at least two values; if there is only one
value, the aspect does not vary, and it is a constant, not a variable. Each value of
an independent variable is called a level of the variable.
– Example:
1) Acoustic condition
– 2) Effect of treatment on shoulder pain

6. Active and Assigned Variables:
– Some independent variables allow the researcher to have complete control.
For example, if a scientist-practitioner is comparing the effects of two different
treatments on a population of 12-year-old children with autism
– there are some conditions of interest in which participants cannot be randomly
assigned or the researcher can choose but not control.
For example, motor ability in children with cerebral palsy compared with
children with typical motor ability

7. 2) Dependent Variable:
– Dependent variables are the outcomes of a study, whether clinical intervention
or not. In the case of clinical intervention, they are the behaviors we wish to
help change. They are dependent because their values depend on changes in
the independent variable.
– It is critical to recognize that, for purposes of an experiment, a dependent
variable must be operationally defined. That is, the researcher must decide how
to measure the outcome. It is not enough to say that range of motion is being
measured; the metric used (degrees, in this case) must be specified. Likewise, it
is not enough to measure “fluency”; the researcher must specify how the value
will be determined (e.g., by counting the number of dysfluencies per 100
words).

8. Intervening Variable:
– Hegde7 describes a type of variable he labels “intervening.” These are largely
mental processes that supposedly “intervene” between input and outcome.
Examples are intelligence, motivation, and executive function.
– We do not deny the existence of these processes and they are extremely
difficult to measure, if measurable at all. Thus, their experimental value is
questionable at best.

9. Confounding and Extraneous
Variables:
– One of the goals of experiments as we currently construct them is to be able to
validly pinpoint the cause-and-effect relationship between independent and
dependent variables.
Point to remember:
When researchers do not, or cannot, control extraneous variables, the study is
vulnerable to various threats to its internal validity.

10. Functional Relationship:
– Functional relationships are easily depicted by graphs, which often facilitate
understanding of the relationship. Graphs in most rehabilitation research are
two-dimensional, with a horizontal (X) axis (the abscissa) showing independent
variables and a vertical (Y) axis (the ordinate) showing the dependent variable.

11. References:
1. Linacre JM, Heinemann AW, Wright BD, et al: The structure and stability of the Functional Independence Measure, Arch Phys Med Rehabil 75:127–
132, 1994.
2. Ryan S: The effects of a sound-field amplification system on managerial time in middle school physical education settings, Lang Speech Hear Serv
Schools 40:131–137, 2009.
3. Hinman RS, Heywood SE, Day AR: Aquatic physical therapy for hip and knee osteoarthritis: results of a single-blind randomized controlled trial, Phys
Ther 87:32–43, 2007.
4. Koutsoftas AD, Harmon MT, Gray S: The effect of Tier 2 intervention for phonemic awareness in a response-tointervention model in low-income
preschool classrooms, Lang Speech Hear Serv Schools 40:116–130, 2009.
5. Harcourt School Publishers: Scientific Research Base, Harcourt Trophies, Orlando, Fla, 2002, Author.
6. Invernizzi M, Sullivan A, Meier J: Phonological Awareness Literacy Screening for Preschool, Charlottesville, Va, 2001, University Press.
7. Hegde MN. Clinical Research in Communicative Disorders, ed 3, Austin, Texas: Pro-Ed; 2003.
8. Nelson LK: Research in Communication Sciences and Disorders, San Diego, 2009, Calif: Plural Publishing.
9. Goldstein EA, Heaton JT, Stepp CE, Hillman RE: Training effects on speech production using a hands-free electromyographically controlled
electrolarynx, J Speech Lang Hear Res 50:335–351, 2007.