Psychology SL Unit 1

Unit 1: Introduction and research methods

Psychology

the study of the behaviour and mental processes of individuals, and how it is affected by an organism’s physical state, mental state, and external environment

Bias

a tendency to perceive information through a cognitive filter of experience and preference. It influences judgements, often in an unfair way. Subjective 

Causality

the cause-and-effect relationship, where the IV alone causes a change in the DV. One event/action (cause) directly proces a change in another event/action (effect)

True experiment

only method to establish a cause-and-effect relationship between two variables

Replication

is when researchers repeat the same process to confirm the reliability of findings. 

It is important to ensure that the results of an experiment can be consistently reproduced. 

Hypothesis

A specific, testable statement that proposes a relationship between variables or predicts an outcome in a research study

Null hypothesis

A statement that argues the IV has no effect on the DV

Research hypothesis

A clear, testable statement that predicts the expected relationship between two or more variables in a study

Independent variable

A variable controlled/manipulated by the researcher

Dependent variable

A variable that is measured, affected by the changes to the IV

Controlled variable

A variable that is kept the same/controlled

Randomisation 

when participants are randomly allocated to conditions

Independent samples design

when participants undergo only one condition

Repeated measures design

when participants undergo both condition

Demand characteristics

Quasi experiment

A research design that aims to evaluate the effect of an IV but lacks random allocation to conditions. There is no causality in this type of experiment.

Natural experiment

an independent variable that is environmental and CANNOT be controlled by the researcher. It is an another type of quasi experiment.

Reliability

consistency of a measure, determines whether the test/measure produces the same results if repeated under the same condition

Validity

accuracy of a measure, determines how accurate the test/measure assesses what it tends to measure

High validity

ensures that meaningful research findings, accurate interpretations, and effective practical applications.

Internal validity

measures how well a study is conducted (its structure) and the accuracy of causality within a specific study. The relationship should not be influenced by other factors/variables

External validity

measures how applicable the findings are in the real world

(how well the study results can be generalised to other situations/groups/events)

Population validity

whether or not the study results can be generalised to other groups of people (larger population of interest). Type of external validity.

Ecological validity

whether or not the study results can be generalised to other situations or settings (real-life settings). Type of external validity.

Artificiality

the degree to which the research condition/task/stimuli/concepts are artificial, rather than occurring naturally in the real world. Consider when measuring the level of ecological validity. 

Mundane Realism

the degree to which the material/procedure involved in an experiment resembles (is similar) to a real-life situation. Consider when measuring the level of ecological validity.

Representative sample

a sample that reflects the diversity of a population

Selection bias

a systematic error that occurs when the participants selected for a study are not representative of the target population, leading to skewed/inaccurate conclusions. For example, when the participants are outliers.

Self-selected sample

participants volunteer to join, by responding to an advertisement, online post, or public notice. It is a sampling technique in quantitative research.

Advantage: convenient and quick

DIsadvantage: often biased: low external validity

Opportunity sample

participants are chosen because they are easily available. For example, people walking by, students in a classroom, colleagues in a workplace. It is a sampling technique in quantitative research.

Advantage: convenient and quick

DIsadvantage: often biased: low external validity

Random sample

every member of the target population has an equal chance of being selected to participate. It is a sampling technique in quantitative research.

Advantage: high external validity and controls for selection bias.

Disadvantage: requires a full list of the population, which may not be possible. Time consuming and often not practical. 

Snowball sample

participants recommend other participants to join a study.

Stratified sample

a probability sample where the participants are randomly selected after divided into subgroups on a shared characteristics, such as age, income, and gender. It is a sampling technique in quantitative research. 

Advantage: high external validity and controls for selection bias.

Disadvantage: complex and time consuming 

Target population

the group of people that researchers WANT to investigate

sample

the group of people that researchers WILL investigate in their research

Quantitative data

data that is numeric, measurable, and CAN be statistically analysed. Obtained in some observations or as part of a case study.

Qualitative data

data that is non-numeric and has descriptive information, and CANNOT be statistically analysed. Often collected through interviews, case studies, or open-ended surveys.

Cross-sectional data

data collected at one point in time

Pros: shorter and faster 

Cons: more inaccurate

Longitudinal data

data collected over multiple time points

Pros: more accurate 

Cons: takes a lot of money and time

CARDUD

Informed Consent, Anonymity, Right to withdraw, Deception, Protection from Undue stress or harm, Debriefing

Informed consent

Participants must be fully informed about the nature, purpose, and potential risks of the study before agreeing to participant. They must voluntarily agree to participate without coercion. 

Special situations: consent by proxy and assent by children 

Anonymity 

Identifying information about participants are NOT recorded or NOT connected to their data, ensuring their privacy is protected 

Special situation: In small/specialised populations, even anonymised data can be indirectly identifying 

Right to withdraw

Participants must be informed that they can stop participating at any time without penalty or negative consequences.

In cases where they have even paid, they are allows to keep their compensation