Experiments And Statistics Flashcards
(38 cards)
Experimentation begins by
formulating a number of research hypotheses.
Translate the different research hypotheses into a set of
treatment conditions and the selection of an appropriate experimental design within which to embody the different treatment conditions
Different treatments are administered to different groups of
subjects or to the same subjects in different orders and performance on some response measure is observed and recorded
Designing experiments
- Experimentation begins by formulating a number of research hypotheses.
- Translate the different research hypotheses into a set of treatment conditions and the selection of an appropriate experimental design within which to embody the different treatment conditions
- Different treatments are administered to different groups of subjects or to the same subjects in different orders and performance on some response measure is observed and recorded.
The treatment variable is commonly known as an
Independent variable
The measure is known as the
Dependent variable
An independent variable is the variable that is
Manipulated
Drug / Placebo
The dependent variable is the response measure which is
manipulated on the basis of the independent variables
Blood sugar levels
There are three kinds of independent variables:
- Quantitative variables are variables that represent variation in amount (e.g. amount of drug, loudness of noise).
- Qualitative variables represent variations in kind or type (e.g. teaching strategy).
- Classification variables systematically vary characteristics which are intrinsic to the subjects of the experiment (e.g. age, sex, IQ, species, word type, etc.)
Quantitative variables are variables that
represent variation in amount (e.g. amount of drug, loudness of noise).
A type of independent variable
Qualitative variables represent
variations in kind or type (e.g. teaching strategy).
A type of independent variable
Classification variables systematically vary
characteristics which are intrinsic to the subjects of the experiment (e.g. age, sex, IQ, species, word type, etc.)
Independent variable
Nuisance variables are potential
independent variables which if left uncontrolled could exert a systematic influence on the different treatment conditions.
Types of nuisance variables
- Several researchers running the same experiment might produce an experimenter effect.
- The time of day could have an influence.
- The kind of subject selected can effect the influence of the independent variables.
(Nusaince variable)
If we do not control for these differences in experimental situation…
we might have a confounding variable in the experiment
Once we have designed an experiment and have produced an experimental hypothesis then we need to decide upon
the specific details of the experiment.
The idea is to select a measure that will
capture” the hypothesised differences.
The measure that is adopted is known as the
Dependent variable
We hypothesise that the observed data will be somehow
dependent on the nature of the independent variable
Control in experimentation
- Consider an experiment where the data is collected by running the experiment simultaneously in two different laboratories:
- The two labs are identical in every respect except that the temperature for each room cannot be controlled.
- Temperature variations may lead to systematic variations in the performance on a task.
- Randomly allocating different treatment conditions to the rooms gives an equally likely “chance” that different random temperatures will be associated with the different treatment means.
Completely randomised designs
- The completely randomized design is characterized by the fact that the subjects are randomly assigned to serve in one of the treatment conditions.
- This is also known as a between subjects design since any differences in behaviour observed among the treatment conditions are based on differences between different groups of subjects.
Randomised block design uses
blocks of subjects who are matched closely on some relevant characteristic
- A common procedure is to treat a subject as a ‘block’, wherein the subject serves in all the treatment conditions of an independent variable.
- When subjects complete all the treatment conditions this type of design is commonly referred to as a repeated measures design or a within subjects design.
Statistical Hypothesises
5
- The Null Hypothesis
- The Alternative Hypothesis
- Deciding to Accept or Reject the Null Hypothesis.
- Errors in Hypothesis Testing.
- Juggling Type I and Type II Errors
A research hypothesis is a
fairly general statement about the assumed nature of the world that gets translated into an experiment.