Posted in AP Psychology


Statistical methods can be divided into descriptive and inferential statistics.

Descriptive statistics summarize data, whereas inferential statistics allow researchers to test hypotheses about data and determine how confident they can be in their inferences about the data.

Descriptive statistics

They do not allow for conclusions to be made about anything other than the particular set of numbers they describe.

Central Tendency —- they characterize the typical value in a set of data. (mean, mode, and median)

The mean —- the arithmetic average of a set of numbers

The mode —- the most frequently occurring value in the data set.

The median —- the number that falls exactly in the middle of a distribution of numbers.

These statistics can be represented by a normal curve

The graph of the normal distribution depends on two factors —- the mean (decide the location of the center of the graph) and the standard deviation (decides the height and width of the graph).

A positive skew —- most values are on the lower end, but there are some exceptionally large values. This creates a “tail” or skew toward the positive end.

A negative skew —- most values are on the higher end, but there are some exceptionally small values. This creates a “tail” or skew toward the negative end.

Although the mean, the mode, and the median give approximations of the central tendency of a group of numbers, they do not tell us much about the variability in that set of numbers.

Variability —- how much the numbers in the set differ from one another.

Standard Deviation —- a function of the average dispersion of numbers around the mean and is a commonly used measure of variability.

Percentile —- express the standing of one score relative to all other scores in a set of data.

It is used frequently when reporting scores on standardized test.

We need statistical techniques to describe how the attributes we are studying relate to one another.

Correlation coefficient —- a numerical value that indicates the degree and direction of the relationship between two variables.

Correlation coefficients range from +1.00 to -1.00.

The sign (+/-) indicates the direction of the correlation, and the number (0 to +/- 1.00) indicates the strength of the relationship.

Pearson correlation coefficient — a descriptive statistic that describes the linear relationship between two attributes.

Pearson correlations can be positive, zero, or negative and are typically measured on a scale ranging from 1 to 0 to -1

From the picture above, we could see that a correlation may be graphed using a scatter plot. The closer the points come to falling on a straight line, the stronger the correlation.

Line of best fit (regression line) — the line drawn through the scatter plot that minimizes the distance of all the points from the line.

Inferential Statistics

Inferential statistics —- used to determine our level of confidence in claiming that a given set of results would be extremely unlikely to occur if the result were only up to chance.

Sample —- the small group of people in the experiment

Population —- the large group to whom the psychologist is trying to generalize

Representative —- the sample reflects the characteristics

Sample size —- number of observations or individuals measured.

Null hypothesis —- a treatment had no effect in an experiment

Alternative hypothesis —- the treatment did have an effect.

Inferential statistics allow us the possibility of rejecting the null hypothesis with a known level of confidence, that is, of saying that our data would be extremely unlikely to have occurred were the null hypothesis true.

Alpha (p value)— the accepted probability that the result of an experiment can be attributed to chance rather than the manipulation of the independent variable.

Given that there is always the possibility that an experiment’s outcome can happen by chance, no matter how improbable, psychologists usually set alpha at 0.05, which means that an experiment’s results will be considered statistically significant if the probability of the results happening by chance is less than 5 percent.

Two types of errors

Type I Error —- the conclusion that a difference exists when in fact this difference does not exist.

Type II Error —- the conclusion that there is no difference when in fact there is a difference.

Psychologists pay particularly close attention to Type I error because they want to be conservative in their inferences: they do not want to conclude that a difference exists if in fact it does not.

The null is trueThe null is False
Fail to reject the nullCorrect decisionType II Error
Reject the nullType I errorCorrect decision

Ethics In Research

Psychological experiments involve deception, which might bias results. The deception is typically small, but in rare instances it can be extreme.

In 1970s, Stanley Milgram conducted obedience experiments in which he convinced participants that they were administering painful electric shocks to other participants, when, in fact, no shocks were given.

Also, you could click this link to know more about the experiment.

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In conclusion, this experiment was unethical because the participants were not aware of the nature of the study and could have believed that they had done serious harm to other people.

After this experiment, ethical standards have been set forth by the American Psychological Association (APA) to ensure the proper treatment of animal and human subjects.

Institutional Review Board (IRB) asses the research plans before the research is approved to ensure that it meets all ethical standards.

Human Research

Informed consent —- participants agree to participate in the study only after they have been told what their participation entails.

Participants are also allowed to leave the experimental situation if they become uncomfortable about their participation.

Debriefing —- after they experiment is concluded, participants must receive it, in which they are told the exact purpose of their participation in the research and of any deception that may have been used in the process of experimentation.

Confidentiality —- the researcher will not identify the source of any of the data.

Many experiments involve collecting sensitive information about participants that the participants might not want to be revealed. For this reason, most psychological data is collected anonymously, with the participant’s name not attached to the collected data. If such anonymity is not possible, it is the researcher’s ethical obligation to ensure that names and sensitive information about participants are not revealed.

Risk —Participants cannot be placed at significant mental or physical risk.

No Coercion — Participants should be voluntary.

Animal Research must meet the following requirements:

— They must have a clear scientific purpose
— The research must answer a specific, important scientific question
— Animals chosen must be best-suited to answer the question at hand.
— They must care for and house animals in a humane way.
— They must acquire animal subjects legally. Animals must be purchased from accredited companies. If wild animals must be used, they need to be trapped in a humane manner.
— They must design experimental procedures that employ the least amount of suffering feasible.

Subfields in Psychology

Applied Psychology —- psychology put directly into practice.

For example: when a therapist meets with a client/ school psychology

Basic psychology —- grounded in research and is often conducted at universities and private laboratories.

Industrial psychology —- the study of human organization and the application of these principles in solving the complex problems present in a variety of workplaces.

Psychiatry — the study of mental disorders, and its practitioners are medical doctors who can prescribe medication, whereas “psychology” is a much broader category.

Other subfields

  • Experimental
  • Developmental
  • Cognitive
  • Social psychology
Posted in AP Psychology

Methods and Approaches

Experimental, Correlational, and Clinical Research

An experiment is an investigation seeking to understand relations of cause and effect.

The manipulated variable is called independent variable

The dependent variable is what is measured.

In order to draw conclusions about the result of the controlled experiment, it is important that certain other conditions are met.

The researcher identifies a specific population, or group of interest, to be studied. Because the population may be too large to study effectively, a representative sample of the population may be drawn.

Experimental group: the group receiving to the independent variable.

Control group: the group does not receive the independent variable but should be kept identical in all other respects.

Representativeness is the degree to which a sample reflects the diverse characteristics of the population that is being studied.

Random sampling is a way of ensuring maximum representativeness

Once sampling has been addressed, subjects are randomly assigned into both the experimental and control groups. Random assignment is done to ensure that each group has minimal differences.

Sampling Bias

Bias of Selection

It occurs when people are selected in a physical space.

For example, if you wanted to survey college students on whether or not they like their football team, you could stand on the quad and survey the first 100 people that walk by. However, this is not completely random because people who don’t have class at that time are unlikely to be represented.

Self-selection Bias

It occurs when the people being studied have some control over whether or not to participate.

A participant’s decision to participate may affect the results.

For example, an Internet survey might elicit responses only from people who are highly opinionated and motivated to complete the surveyP

Pre-screening or advertising bias

It occurs often in medial research; how volunteers are screened or where advertising is placed might skew the sample.

For example, if a researcher wanted to prove that a certain treatment helps people to stop smoking, the merce act of advertising for people who “want to quit smoking” might provide only a sample of people who are already highly motivated to quit and might have done so without the treatment.

Healthy user bias

It occurs when the study population tend to be in better shape than the general population

As with the bias of selection from a specific real area, this is an instance in which those subjects might not, in turn, accurately represent their neighborhoods —- even though they gym might have a diverse population.

Researchers use a single- or double-bind design to avoid inadvertently influencing the results.

Single-blind design —-the subjects do not know whether they are in the control or experimental group.

Double-blind design —-neither the subjects nor the researcher knows who is in the two groups.

Double-blind studies are designed so that the experiment does not inadvertently change the responses of the subject, such as by using a different tone of voice with members of the control group than with the experimental group.

In some double-blind experiments, the control group is given a placebo —- a seemingly therapeutic object or procedure , which causes the control group to believe they are in the experimental group but actually contains none of the tested material.

Correlational research —- assessing the degree of of association between two or more variables or characteristics of interest that occur naturally. I

In this type of design, researchers do not directly manipulate variables but rather observe natural-ly occurring difference. 

Correlation does not prove causation; correlation simply shows the strength of the relationship among variables.

  • For example, poor school performance may be correlated with lack of sleep. However, we do not know if lack of sleep caused the poor performance, or if the poor school performance caused the lack of sleep, or if some other unidentified factor influenced them both.

Confounding variable: an unknown factor is playing a role, a third variable, or an extraneous variable.

Through surveys (questionnaires or interviews) —- One way to gather information for correlational studies

Correlational studies can be preferred to experiments because they are less expensive not as time consuming, and easier to conduct.

In addition, some relationships cannot be ethically studied in experiments.

  • For example, you may want to study how child abuse affects self-efficacy in adulthood. But no one will allow yo to randomly assign half of your baby participants to the child abuse condition

Two types of research

Longitudinal studies —- happen over long periods of time with the same subjects (e.g. studying the long-term effects of diet and exercise on heart disease)

Cross-sectional studies —- to test a wide array of subjects from different backgrounds to increase generalizability.

Case studies

They are intensive psychological studies of a single individual.

These studies are conducted under the assumption that an in-depth understanding of single cases will allow for general conclusions about other similar cases.

To investigate the circumstances of the life of notable figures in history.

Researchers must be careful though, because case stud-ies, like correlational ones, cannot lead to conclusions regarding causality. 

Sigmund Freud and Carl Rogers used numerous case studies to draw their conclusions about psychology.

Danger of assessing the outcome of case studies is that the individual studied may be atypical of the larger population.

Therefore, researchers try to ensure that their studies are generalizable —- applicable to similar circumstances because of the predictable outcomes of repeated tests.

Experimental Design

Conceptual definition —- the theory or issue being studied.

Operational definition —- the way in which that theory or issue will be directly observed or measured in the study.

Operational definition have to be internally and externally valid.

Internal validity —- the certainty with which the results of an experiment can be attributed to the manipulation of the independent variable rather than to some other, confounding variable.

External validity — the extent to which the findings of a study can be generalized to other contexts in the “real world”

—- It is also significant that the study have reliability —- whether or not the same results appear if the experiment is repeated under similar conditions.

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Eight Different Approaches’ usage

Biological Approach

  • Question: How is the physiology of high risk-takers different from that of non-risk-takers?
  • Cause of Behavior: Physiology
  • Methods: Brain scans

Behavioral genetics

  • Which genes contribute to the development of risk-taking?
  • Cause of Behavior: Genes
  • Methods: Genetic analysis


  • How does rewarding or punishing a risk-taker affect his or her behavior?
  • Cause of Behavior: Learning and reflexes
  • Methods: Behavior modification


  • How do risk-takers think and solve problems?
  • Cause of Behavior: Thoughts
  • Methods: Computer models of memory networks


  • How does the adolescent’s self-esteem encourage or discourage risk-taking behavior?
  • Cause of Behavior: Self-concept
  • Methods: Talk therapy


  • How might a child’s early experiences affect risk-taking in adolescence?
  • Cause of Behavior: Unconscious mind
  • Methods: Dream analysis, talk therapy


  • How might an adolescent’s culture lead to risk-taking
  • Cause of Behavior: Cultural environment
  • Methods: Cross-cultural studies


  • Is risk-taking an evolutionary adaptive trait?
  • Cause of Behavior: Natural selection
  • Methods: Species comparison
Posted in AP Psychology

Notes of AP Psychology

History and Approaches of Psychology

Psychology is the study of BEHAVIOR and the MINDBEHAVIOR, a natural process subject to natural laws, refers to the observable actions of a person or an animal. MIND refers to the sensations, memories, motives, emotions, thoughts, and other subjective phenomena particular to an individual or animal that are not readily observed.

Psychology is a SCIENCE because it uses systematic observation and collection of data to try to answer questions about the mind and behavior and their interactions.

Socrates considered the philosophical issues of beauty, justice , and human rights. Plato, a student of Socrates argued that humans posses innate knowledge that is not obtainable simply by observing the physical world. Aristotle, a student of Plato, believed that we derive truth from the physical world. His application of logic and systematic observation of the world laid the basis for the scientific method.


  •  Greeks thought that the world and all things were divided into two parts: body and spirit.
  • It is a theme that recurs often in psychology.
  • The distinction between body and spirit mirrors the current debate around the difference between the BRAIN (the command center of the central nervous system [CNS]) and the MIND (the sensation memories, emotions, thoughts, and other subjective experiences of a particular individual)

René Descartes (1596-1650)

  • He conducted some of the most important speculations on human nature.
  • He believed that the physical world is not under divine influence but rather follows a set of observable laws or rules. 
  • He believed that humans were the exception to this rule because they posses minds which is not observable and is not subject to natural laws.
  • “The mind controls the body.”
  • He believed that the interaction of the body and the mind occurs in the pineal gland, which is located deep within the brain at the top of the brain stem.
  • Finally, he realized that some body movements, which he named reflexes, are not controlled by the mind. 
  • Reflex —- an immediate, unconscious reaction to an environmental event, such as pulling your hand away from a flame.

John Locke (1632-1704)

  • He believed that event the mind is under the control of such laws.
  • Empiricism 
    • the acquisition of truth through observations and experiences.

Human are born knowing nothing.

Essay Concerning Human Understanding
  • Tabula rasa (Latin for “blank slate”) to describe the mind of an infant. 
  • All knowledge must derive from experience.
  • Nurture over nature as the greater influence on development.

Thomas Hobbes (1588-1679)

  • He believed that the idea of a soul or spirit, or even of a mind, is meaningless.
  • Materialism 
    • the belief that the only exist are matter and energy.
    • Greatly influences behaviorism.
  • Our experience is a by-product of the machinery of the brain.

The 19th century was a time of treat discovery in biology and medicine. They theory of natural selection, a new theory revolutionized science, claimed by Charles Darwin (1809-1882). He published book On the Origin of Species in 1859.
  • He proposed a theory of natural selection 
    • All creatures have evolved into their present state over long periods of time.
  • Overtime, this process selects physical and behavioral characteristics that promote survival in a particular environment.

Evolutionary theory set the stage for psychology by providing a way to explain differences between species and justifying the use of animals as a means to study the roots of human behavior.
  • He is the founder of the science of psychology because he set up the first psychological laboratory in an apartment near the university at Leipzig, Germany. 
  • He used this laboratory to study the mind.
  • Wundt wanted to examine basic cognitive structure, so he made a interview process called Introspection:
    • The subjects were asked to record accurately their cognitive reactions to simple stimuli.

Edward Titchener (1867-1927)

  • He was a student in Wundt’s laboratory and was one of the first to bring the science of psychology to the United States.
  • Structuralism
    • It was used to understand the structure of mind.
    •  the idea that the mind operates by combining subjective emotions and objective sensations. 
  • Introspection
    • the subjects were asked to record accurately their cognitive reactions to simple stimuli.
  • Introspective theories were important in establishing the science of psychology, but they do not significantly influence current psychological thinking.

Interestingly, in the Princeton version of AP Psychology book, it separate Edward Titchener and Wilhelm Wundt into two parts; however, in the Barron’s version of AP Psychology book, it is said that the structuralism and introspection belong to Wundt. For me, if the answer or question include both Wundt and Titchener, then we should choose Wundt. If only Edward Titchener appear on the answer, then we should choose him.

William James (1842-1910)

  • An American psychologist who opposed the structuralist approach.
  • Heavily influenced by Darwin
  • Functionalism
    • He believed that the significant thing to understand is how the mind fulfills its purpose.

Others who associate with William James

Mary Whiton Calkins (1863-1930)

She studied with William James and went on to become president of the American Psychological Association (APA).

Margaret Floy Washburn (1871-1939)

She was the first woman to earn a Ph.D in psychology (because woman don’t have some rights at that time).

G. Stanley (1844-1924)

  • He was the student of William James.
  • He pioneered the study of child development.
  • He was the first president of American Psychological Association (APA)


Approach 1: Biological 

Biological psychology seeks to understand the interactions between anatomy and physiology and behavior. In the field, researchers use some devices, CAT scans, MRIs, EEGs, or PET scans, to help them to do the experiment.

Approach 2: Behavioral Genetics

Behavioral genetics emphasizes that particular behaviors are attributed to specific, genetically based psychological characteristics. 

Approach 3: Behavorial

Behaviorism posits that psychology is the study of observable behavior. Therefore, behaviorists do not care about the mind or mental event because it cannot be observed.  They think that psychologist should only consider stimuli (environmental events) and responses (physical reactions).

There are some important people:

Ivan Pavlov (1849-1936)

  • Classical conditioning 
    • A basic form of learning in which a behavior comes to be elicited by a formerly neutral stimulus.
    • One of the important findings of behaviorist.

John Watson (1878-1928)

He and his assistant Rosalie Rayner applied classical conditioning to humans in the famed Little Albert experiment. 

One of his famous sentence:

Give me a dozen healthy infants, well-formed ,and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select — doctor, lawyer, artist, merchant-chief and, yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.

John B. Watson

B.F. Skinner (1904-1990)

  • He described operant conditioning in which a subject learns to associate a behavioral response with an environmental outcome by using his Skinner Box.
  • Reinforcement
    • environmental stimuli that either encourage or discourage certain responses.

Many behavioral principles are still used in behavior modification —- a set of techniques in which psychological problems are considered to be the product of learned habits, which can be unlearned by the application of behavioral methods.

Approach 4: Cognitive

Cognitive psychology is that to understand people’s behavior, we must first understand how they think.

  • This approach combines both the structuralist approach —- looking at the subcomponents of thought —- and the functionalist approach —- understanding the purpose of thought.
  • Use variety of methods: reaction-time tasks, computer models, and participants’ self reports, to better understand thought.
  • Largely replaced the behavioral approach as the predominant psychological method used in the United States. Also, it remains popular today, and this approach has influenced and blended with others.

Approach 5: Humanistic

Humanistic approach is rooted in the philosophical tradition of studying the roles of consciousness, free will, and awareness of the human condition. 

  • A holistic study of personality that developed in response to a general dissatisfaction with behaviorism’s inattention to the mind and its function.
  • It emphasize personal values and goals and how they influence behavior, rather than attempting to divide personality into smaller components.

Abraham Maslow (1908-1970)

  • Self-actualization
    • the need for individuals to reach their full potential in a creative way.
    • Attaining it means accepting yourself and your nature, while knowing your limits and strengths.

A musician must make music, an artist must paint, a poet must write, if he is to be ultimately at peace with himself.

Abraham Maslow

Carl Rogers (1902-1987)

He stressed the role of unconditional positive regard in interactions and the need for positive self-concept as critical factors in attaining self-actualization.


They contrasts with the deterministic behaviorist, who theorized that all  behaviors are caused by past conditioning. 

Humanists believe that we choose most of our behaviors and these choices are guided by physiological, emotional, or spiritual needs. 

  • e.g. Humanistic psychologist might explain that an introverted person may choose to limits social contact with other because he or she finds that social needs are better satisfied by contact with a few close friends rather than large groups.

Humanistic ideas are helpful in aiding clients to overcome obstacles in their lives.

Approach 6: Psychoanalytic/Psychodynamic

Sigmund Freud (1856-1939)

  • Psychoanalytic theory
    • A theory of human behavior 
  • He drew a distinction between the conscious mind —- a mental state of awareness that we have ready access to —- and the unconscious mind  —- those mental processes that we do not normally have access to but are yet influenced by in some way.

Psychoanalytic theory stresses the importance of childhood experiences and a child’s relationship with his or her parents to the parents to the development of personality.

The focus of the psychoanalytic approach is on the resolution of unconscious conflicts through uncovering information that has been repressed, or buried in the unconscious.

Carl Jung (1875-1961)

He later expanded on the psychoanalytic theory with his concept of the collective unconscious, a part of the individual’s unconscious which derives memory and knowledge from an ancestral memory, common to the human experience.

Approach 7: Sociocultural

Those subscribing to the sociocultural approach believe that the environment a person lives in has a great deal to do with how the person behaves and how others perceive that behavior. 

According to this approach, cultural values vary from society to society and must be taken into account when trying to understand, predict, or control behavior. 

Because different people are born in the different sociocultural background so that people have different mind to do different behavior. In other word, if you want to deeply understand the writer of the book, you have to look his or her background.

Approach 8: Evolutionary

The evolutionary approach focuses on the theories of Darwin. Behavior can best be explained in terms of how adaptive that behavior is to our survival. 

  • For example, fear is an adaptive evolutionary response; without fear, our survival would be jeopardized (endangered).

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