Unit 1: Introduction to research (IB HL Psych)

Experiments, sampling techniques, limitations, ethics

Comfirmation Bias

Existing belief is confirmed - for example, I won a game wearing red socks, so I must wear red socks again.

Stereotype effect

Believe something that affects out performance - for example, girls are bad at math, so they don’t try as hard

Cause and effect

Relationship between 2 variable, where 1 variable causes an effect on another variable

Hypothesis

Specific and testable statement that proposes a relationship between variables or predicts an outcome in a research study.

Null hypothesis (Ho)

Argues that IV had no effect on DV, we often want to prove this hypothesis wrong using experimental data.

Alternative hypothesis (Ha or H1)

Argues that there is a relationship between IV and DV, or a statistically significant effect between variables. Wants to prove the Null Hypothesis wrong.

Dual coding theory

Processing and recall is better if information is presented in two forms (for ex- image and words)

True experiments

• Establishes cause and effect relationship

• Participants randomly allocated

• Investigates the relationship between IV and DV by measuring

• Highly standardized procedures so that other researchers can replicate

To make study of human behavior specific

1. Falsifiable

2. Replicable for others

3. Empirical evidence

Experimental hypothesis

Precise and testable prediction about a predicted outcome in a study

One tailed hypothesis

A specific direction for effect of IV on DV, and effect is significantly greater or less than what is predicted by Null hypothesis (Coffee causes positive performance)

Two tailed hypothesis

Hypothesis predicitng statistical significance or relationship between two variables, but no specification of the direction of effect. (Coffee changes performance)

Confounding variables

Variables that disort relationship between IV and DV (must be controlled or it will contribute to bias)

Quasi-experiment

• IV is usually something hte patient already has (gender)

• IV can be manipulated

• Not randomized because groups are pre-existing instead of random allocations, no random allocations

• Casuality can’t be determined

Operationalization

Define variables, and detailed explanation on how IV or DV is measured in the study.

Natural experiment

• Takes advantage of naturally occuring event to obersve DV (natural disasters for example)

• Subjects cannot be randomly allocated to experrimental groups

• Higher external validity because it reflects real world behavior

• Can’t manipulate IV because its naturally existing (For example, Laws)

Target population

the group being studied

ex: all high school students worldwide

Sample population

group representing target population (likely be in experiment)

ex: kanto plain high school students

Participants

group who will actually take part in the research (smaller population taken from sample)

Sampling technique

Is used to find a sample group that can be generalized to the target population (external validity)

Population validity

The extent which findings can be generalized from the sample to the target population. It is high when appropriate sampling technique used as it represents target population.

External validity types

1. Population validity

2. Ecological validity

Ecological validity

The extent which findings can be generalized from the experiments to other settings or situations. If the procedures are more artificial and standardized (avoids bias and confounding variables), the validity is higher

Selection Bias

When participants are not representitive of the larger population being studied.

Causes of selection bias

• Participants self-select/volunteer

• Researcher intentionally/unintentionally chooses certain type of person

• Certain groups (eg: disabled) excluded from sample because of how participants are recruited (eg: ads)

Self-selected (sampling technique)

By posters, advertisements, newspapers, online posts, public notices

• Advantage: Convenient

• Disadvantage: Biased, low external validity

Oppurtunity (sampling technique)

Participants chosen because they are available. For example, you ae walking by a metro and asked for an interview. You are already there at the place the research is being conducted.

• Advantage: Convenient and quick

• Disadvantage: Biased, low external validity

Random Samples (sampling technique)

Every individual in target population has equal chance of being selected to participate

• Advantage: High external validity, controls selection bias

• Disadvantage: Requires full list of population so its time consuming and not practical or possible

Field experiment

• Conducted in real world/natural settings rather than controlled laboratory experiment

• Cause and effect relationship

• Reduced reactivity

• Can manipulate IV and take place in a natural setting

Experimental research design

• Repeated measures design

• Independent samples design

• Matched pairs design

Stratified sampling

A probability sample where population is divided into subgroups based on shared characteristics (ex: gender) then randomly selected in proportion to their presence in overall population

• Advantage: High external validity

• Disadvantage: Complex and time consuming

Matched pairs design

Participants are grouped based on similar characteristucs then randomly allocated.

• Reduces variability

They could also be pre-tested based on a variable (memory) then allocated to conditions.

Independent measures design

2 or more seperate groups of participants where each group take part in only 1 condition of the experiment.

Repeated measures design

The same participants take part in all conditions of an experiment (compares through performance across)

Representational Generalization

Order of population (from participant to population)

Population > Target population > Accessible population > Sample > Participant

• Accessible population is when it’s available to the researcher

• Sample size is selected by sampling methods.

Why students are not easily generalized to wider population

Different experience

• Age

• Socioeconomic status

• Education level

• Life experience

• Tend to be more verbal and social