Validities
Describe a situation Describe a situation
Term Definition that benefits that detriments
[term]. [term].
Reliability The extent to which a When you obtain the When you ask some
(when measurement is free same results from a of the respondents to
measuring a from random group with fill in your
construct) measurement errors. independent questionnaire, and
This means that the measurements at there is a lot of noise
scores are different times, with nuisance due to the
independent of time, the same construction of the
place and measurement tool. new tram line.
environment.
Construct The extent to which In the case of a When a questionnaire
validity the instrument questionnaire on a for measuring
(operationalization) sensitive subject, the loneliness does not
succeeds in questions are contain items about
measuring the formulated in such a social loneliness, but
construct and thus fits way as to limit the only items about
the conceptual tendency to answer emotional loneliness
definition. socially desirable. (content-validity).
Internal The extent to which You carry out an You have developed a
validity the research method experiment in which program to improve
can eliminate everything (except children's spatial
alternative the dependent perception. To
explanations for an variable) is controlled. investigate the effect
effect/relationship. of the program you
use a pre- and post-
test. For both tests
you use the same
puzzles.
-> The research
question cannot be
answered correctly.
Do children do the
puzzles in the post-
test better because of
the program or
because they have
remembered the
puzzles (testing)?
External The extent to which The sample is You want to do
validity the research results representative of the research into the
can be generalized to population. extent of television
other populations, watching among
settings and times. young people. You will
therefore take a
questionnaire with 40
boys you meet at the
, mall.
-> This is a limited
sample, which makes
it difficult to
generalize the results
to the population
(young people).
Statistical The extent to which A researcher uses a A researcher reports a
validity the results of a certain data analysis significant difference
statistical analysis are technique only after in means on the
accurate and well- he has checked dependent variable in
founded. whether the an experiment, but
corresponding does not present an
conditions/assumption effect size.
s have been met.
Independent observations Observations (data of different participants) should
be independent, basically meaning that the behavior
of one person does not influence the behavior of
another.
Dependent variable should be continuous. The dependent variable should be a continuous
measure (interval or ratio). If a dependent variable is
nominal or ordinal, it is not possible to use linear
regression.
Independent variable should be continuous or The independent variable(s) should be continuous or
dichotomous. dichotomous. A categorical predictor can be
changed into several dichotomous variables
(dummy’s).
Linear relationship between predictors and The relationship between an independent and
dependent variable. dependent variable should be described using a
straight line.
Absence of outliers (in X, Y and XY-space) Outliers should be absent from the data. Outliers
are observations very different from others.
Absence of multicollinearity Independent variables should not be strongly
correlated.
Homoscedasticity The residuals at each level of the independent
variable(s) have similar variances.
Normality distributed residuals Residuals are the differences between the values
predicted by the model and the values observed in
the data om which the model is based. These
differences should be normally distributed.
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