Experimental methods in psychology tutorial
Summary
TLDRThis tutorial covers different types of experiments—lab, field, and quasi experiments—as well as experimental designs such as independent groups, repeated measures, and matched pairs. It explains the strengths and weaknesses of each type, focusing on control of variables, ecological validity, and potential biases like demand characteristics. The session emphasizes understanding the difference between experiment types and designs, including how to handle extraneous variables, minimize participant effects, and implement techniques like counterbalancing to improve the validity of experimental results.
Takeaways
- 🧪 Lab experiments are conducted in controlled environments, allowing researchers to manipulate the independent variable and minimize extraneous variables.
- 👍 One strength of lab experiments is the ability to draw stronger causal conclusions due to minimized extraneous variables.
- 👎 A weakness of lab experiments is that tasks can lack realism, making them less applicable to real-world situations, and participants may show demand characteristics.
- 🌳 Field experiments take place in natural settings, where participants may not know they're part of an experiment, leading to more natural behavior.
- 😊 Field experiments have fewer demand characteristics and greater ecological validity, making the results more generalizable to real-life contexts.
- ⚠️ However, field experiments lack control over extraneous variables and are harder to replicate due to inconsistent conditions.
- 🌿 Quasi-experiments involve naturally occurring independent variables, such as age or gender, with high ecological validity but weaker control over variables and difficulty establishing causality.
- 🚗 Experimental designs include independent groups, repeated measures, and matched pairs, each with its strengths and weaknesses.
- 📋 In independent groups design, participants only engage in one experimental condition, but participant differences between groups may introduce extraneous variables.
- 🔄 Repeated measures design involves the same participants in all conditions, reducing participant variables but potentially introducing order effects like boredom or practice, mitigated by counterbalancing.
Q & A
What is the difference between a type of experiment and an experimental design?
-A type of experiment refers to where and how the experiment is conducted, such as lab, field, or quasi experiments. Experimental design, on the other hand, refers to how participants are allocated to different conditions, including independent groups, repeated measures, and matched pairs designs.
What is a lab experiment, and what are its key strengths?
-A lab experiment is conducted in a controlled environment where the independent variable is deliberately manipulated by the researcher. Its key strengths include control over extraneous variables, allowing for more causal conclusions, and ensuring that the independent variable affects the dependent variable without interference from other factors.
What are the weaknesses of lab experiments?
-Lab experiments can lack mundane realism, meaning the tasks participants perform may be artificial and unrealistic. Additionally, participants may show demand characteristics by behaving in a way they believe the researcher wants them to, potentially skewing the results.
What is a field experiment, and how does it differ from a lab experiment?
-A field experiment is conducted in a natural environment where participants may not know they are part of an experiment. Unlike lab experiments, field experiments have higher ecological validity, as participants behave more naturally, but there is less control over extraneous variables, making it harder to replicate and control results.
What are the strengths of field experiments?
-Field experiments have fewer demand characteristics because participants are often unaware they are part of an experiment, leading to more natural behavior. They also have greater ecological validity, meaning the results can be better generalized to real-life situations.
What is a quasi-experiment and what is its key characteristic?
-A quasi-experiment, or natural experiment, is one where the independent variable is naturally occurring, such as differences in age, race, or gender. The researcher cannot manipulate these variables, making it different from lab or field experiments.
What are the weaknesses of quasi-experiments?
-Since the independent variable cannot be controlled by the researcher, it is harder to establish cause-and-effect relationships. Additionally, quasi-experiments are difficult to replicate because the naturally occurring variables cannot be manipulated.
What is an independent groups design in experimental research?
-In an independent groups design, participants are divided into different groups, each of which only takes part in one experimental condition. For example, one group might participate in condition A, while another group participates in condition B.
What is a repeated measures design, and what are its potential issues?
-In a repeated measures design, all participants take part in all experimental conditions. A potential issue is that participants might experience practice effects, becoming more skilled at a task as they go through the conditions, or become bored and tired, which could affect the results.
What is a matched pairs design, and how does it minimize extraneous variables?
-A matched pairs design attempts to reduce participant variables by pairing participants with similar key characteristics, such as age, IQ, or handedness. Each member of the pair is then placed in a different experimental condition, which helps compare 'like-for-like' and minimize extraneous variables.
Outlines
📚 Introduction to Experiment Types and Designs
The introduction welcomes viewers to the tutorial on research methods, particularly focusing on experiments. It emphasizes taking notes, asking questions, and reading supplementary materials. The tutorial will cover different types of experiments such as lab, field, and quasi-experiments, along with experimental designs like independent groups, repeated measures, and matched pairs. The key distinction between experiment types and designs is introduced, with lab experiments explained as highly controlled environments where the independent variable (IV) is manipulated by the researcher. Advantages like minimizing extraneous variables and drawing causal conclusions are discussed, as well as limitations like lack of mundane realism and demand characteristics, where participants might behave as they think the researcher expects.
🔬 Field and Quasi-Experiments: Strengths and Weaknesses
This section introduces field experiments, which take place in natural environments, allowing for more natural participant behavior due to reduced demand characteristics. The advantages include greater ecological validity, but weaknesses include reduced control over extraneous variables and difficulty in replication. Quasi-experiments, where the IV is naturally occurring (e.g., age, race, gender), are also covered. While they offer high ecological validity, they lack control over the IV and extraneous variables, making it harder to establish cause and effect. Quasi-experiments are also difficult to replicate due to the natural occurrence of variables.
🚗 Understanding Experimental Design: Independent Groups
Experimental design is compared to different types of cars, each with its own strengths and weaknesses. In an independent groups design, participants are divided into separate groups, each experiencing only one experimental condition. This design avoids practice or fatigue effects but introduces potential participant variability between groups. The explanation includes examples of how conditions may vary, such as one group memorizing a list of words and another viewing pictures. The challenges of extraneous variables affecting the results and the advantages of preventing fatigue or practice effects in participants are highlighted.
🔁 Repeated Measures Design: Advantages and Risks
In a repeated measures design, all participants take part in all experimental conditions. This minimizes participant variability since the same individuals are used in each condition. However, issues like practice or fatigue effects can arise, as participants may become better or worse at the task over time. The concept of counterbalancing is introduced as a solution, where the order of conditions is reversed for different groups to mitigate these order effects. This ensures that boredom or practice effects do not skew the results of later conditions in the experiment.
👯♂️ Matched Pairs Design: Reducing Participant Variability
The final section explains the matched pairs design, where participants are paired based on key characteristics (e.g., age, handedness, IQ) to minimize differences between experimental conditions. For example, two participants with similar attributes are assigned to different experimental conditions. While it's challenging to achieve perfect matches, this design helps control for participant variables that might otherwise impact the results. By randomly assigning matched participants to different conditions, researchers aim to compare like-for-like, reducing the influence of extraneous participant variables on the experiment’s outcome.
Mindmap
Keywords
💡Lab Experiment
💡Field Experiment
💡Quasi Experiment
💡Independent Groups Design
💡Repeated Measures Design
💡Matched Pairs Design
💡Extraneous Variables
💡Mundane Realism
💡Demand Characteristics
💡Ecological Validity
Highlights
Recap that the slides marked with a pause button should be included in the notes as a minimum requirement.
Encourages students to add questions or examples related to the material and discuss them in class.
Differentiation between types of experiments (lab, field, quasi) and experimental designs (independent groups, repeated measures, matched pairs).
Lab experiments are conducted in controlled environments where the independent variable is deliberately manipulated by the researcher.
A strength of lab experiments is the ability to minimize extraneous variables, allowing for more reliable causal conclusions.
A weakness of lab experiments is the lack of mundane realism and the risk of demand characteristics from participants.
Field experiments are conducted in natural settings where participants may not be aware they are part of an experiment, leading to more natural behavior.
Field experiments have greater ecological validity but less control over extraneous variables, making them harder to replicate.
Quasi or natural experiments involve independent variables that naturally occur and are not manipulated by the researcher.
Quasi experiments have high ecological validity but make it harder to establish cause and effect and are difficult to replicate.
Independent groups design involves participants only taking part in one experimental condition, reducing practice or fatigue effects.
Repeated measures design involves all participants taking part in all experimental conditions, which minimizes participant variables but may introduce practice or boredom effects.
Counterbalancing in repeated measures design helps reduce order effects by reversing the order of experimental conditions.
Matched pairs design aims to minimize participant variables by matching participants on key characteristics before assigning them to different experimental conditions.
Tutorial concludes with an explanation of how different experimental designs have various strengths and weaknesses, all aimed at minimizing extraneous variables and improving research reliability.
Transcripts
hello everyone welcome to this search
method tutorial about experiments
just to recap these slides with the
pause button need to be in your notes as
a minimum you should also try to add
into your notes some examples or
questions that you might have about the
material that we can discuss these in
class and you could also if you wanted
to start to read around the subject by
following the web links or by having a
look in your textbook
this tutorial will cover the types of
experiments such as lab field and quasi
experiments and also different ways that
we can design experiments which include
independent groups repeated measures and
matched pairs it's really important that
you don't confuse a type of experiment
with an experimental design and we'll
talk about what each of these means as
we go through so lab experiments as the
name suggests are carried out in
controlled lab environments for
psychology purposes a lab could just be
a room with an overhead projector in it
or any pieces of equipment that the
researcher might need here the
independent variable is deliberately
manipulated by the researcher one of the
strengths of a lab experiment is that
extraneous variables can be minimized
because it's carried out in a lab the
researcher has control over the
environment and the time of day the
conditions in which the experiment takes
place so we can make sure that we've
minimized as many of those extraneous
variables as we can another strength is
that because we've minimized those
extraneous variables it allows us to
make more causal conclusions by saying
that the independent variable is the
thing that's affecting the dependent
variable we can be more sure that the IV
is causing the change in the DV and that
nothing else is getting in the way of
that result lab experiments do have
their weaknesses as well one of the
bigger weaknesses is that the
experimental tasks can be said to lack
mundane realism which just means that
they're unrealistic the tasks the
participants are asked to perform in lab
experiments tend to be very artificial
and bear no resemblance to what they
might do in real life another weakness
is that participants might show demand
characteristics which means that they'll
behave in a way they think the
experimenter wants them to behave they
know they're in an experimental
situation so they know that the
experimenter is looking for them to do
something specific they might try to
figure out what the aim of the
experiment is and then either go along
with the researcher or go against what
they're looking to find
any old experiments are carried out in
natural environments so the participants
might not know that they're taking part
in an experiment the independent
variable is still being deliberately
manipulated however these are the kind
of studies that might take place on
school playgrounds or in shopping
centers participants are just going
about their normal nights
one of the strengths of a field
experiment is that there are fewer
demand characteristics because the
participants are unaware often that
they're taking part in an experiment
they won't change their behavior so the
behavior of the participants is much
more natural there's also much greater
ecological validity which means that
because the study takes place in real
life the results can be generalized to
real life
I think these is the opposite of a lab
experiment
you
looking at the weaknesses we have far
less control over the extraneous
variables which might affect my result
it's again it's the opposite really to a
lab experiment these studies can
sometimes be difficult to replicate as
the conditions where the experiment is
carried out won't always be the same so
it will be difficult to carry out the
experiment again in exactly the same
conditions
and the last type of experiment that you
need to know about is a quasi experiment
or sometimes called a natural experiment
this is where the independent variable
is naturally occurring so it's not
manipulated by the researcher these
things like different ages different
races genders we can't actually
manipulate those things as researchers
so they're natural experiments these are
very high ecological validity because
the independent variable is naturally
occurring anyway however in terms of
weaknesses because we've got no control
over the independent variable or any
other extraneous variables it's much
harder to identify cause and effect it's
also next to impossible to replicate
because these naturally occurring
variables cannot be deliberately
manipulated
okay let's look at experimental design
it might help you to think about
experimental design as being different
types of car they're all cars but
they're all constructed and designed
very very differently though have
different strengths and different
weaknesses in the same way there are
different techniques and methods we can
use to put our experiments together and
each of those has strengths and
weaknesses that go with it
in an independent groups design
participants only take part in one of
the experimental conditions so for
example we might have Group one who
would take part in condition a which
might be trying to remember a list of
ten what we could then have group two
who are completely different
participants taking part in condition B
which might be looking at ten pictures
to remember each of these participants
only does one of those conditions
because there are different participants
in each condition think about how this
might present the researcher with
extraneous variables what differences
might there be between the participants
in condition a and the participants in
condition B and one might just be a
problem also they think about the fact
that each participant only takes part in
one of those conditions so they won't
have become bored or tired or even more
practiced by the time they get on to
doing the second third or even fourth
condition in some experiments why might
this be a good thing
okay you know repeated measures design
all of the participants take part in all
of the experimental conditions so here
we'd have one group of participants take
part in condition a and in the very same
group of participants would take part in
condition B okay think about the
questions from the last slide about
boredom or practice effects how might
these affect the results if by the time
the participants get to condition B or
condition C if they've had a lot of
practice at whatever task they're doing
or if they're just bored or tired and
have had enough what effect might this
have on the results of the later
conditions because all the participants
are the same we're comparing like for
like
so we've minimized those participant
variables because we're using a repeated
measures design so we've taken out some
of those extraneous variables one way to
overcome the problem of boredom or
practice effects is called repeated
measures counter balancing so counter
balancing is really just there to reduce
those order effects so here we'd have
participants in condition a and in the
same kind of participants would go on
and do condition B a different group of
participants would start with condition
B and then they would go on to do
condition a so we've reversed the order
and what this means is that we don't
work through the conditions in exactly
the same order so by the time they get
to condition B or C they might have been
bored and this could affect the results
so if some participants start of
condition B we've ruled out that effect
and the last type of experimental design
that you need to know about is called a
matched pairs design and this aims to
reduce the participant variables between
the different experimental conditions by
matching the participants as closely as
possible on some key variables to try
and make each group as similar as
possible so we could have a participant
Sally who's six years old she's
left-handed and she's got an IQ of 90
and we would try and match her with
another similar participant so here
we've got Rosie who's also six years
also left-handed and has a very similar
IQ score they're unlikely to match
completely so we've matched our two
participants and then what we do is
randomly assigned them to an
experimental condition so Sally would be
in condition a and Rosie would be in
condition B and what we've tried to do
is just to ensure that we're still
trying to compare like-for-like and
we've minimized those those extraneous
variables to do with participants and
that's all for this tutorial thanks very
much and I'll see you again soon bye
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