Psychology Chapter 2

Standards for drawing conclusions from Data

Validity and Reliability

third variable

a variable that is responsible for correlation observed between two other variables of interest (one of the reasons that correlation does not cause causation)

Variability

in statistics, the extent to which scores differ from one another or from their mean; often measured using the standard deviation.

Mean

the numerical average of a set of scores, computed by adding all scores together and dividing by the number of scores.

Three ways to study the effects of time

• Cross-sectional design • Longitudinal design • Mixed-longitudinal design

Correlation does not cause causation because

• First, the two variables in a correlation can influence each other simultaneously (although it might be true that playing violent video games leads to physical aggression at school, youth who experience physical aggression at school may be more attracted to violent video games as an outlet for their frustration). • Second, we might be observing a situation in which a third variable is responsible for the correlation we see between our two variables of interest. • A third variable is a variable that is responsible for a correlation observed between two other variables of interest.

How to Develop and Test a Theory

• Theory building begins with generating hypotheses. • The hypotheses are then systematically tested (through systematic observation - either experimental or non-experimental) • Hypotheses that are not rejected contribute to the theory and help generate new hypotheses.

What are the three ways in which scientific method differs from simple observation?

1) Science relies on objectivity rather than subjectivity. 2) Science uses systematic observation as opposed to hit-or-miss observation 3) Science relies on observable, repeatable evidence, whereas everyday observation often ignores evidence, especially when it runs counter to strongly held beliefs.

5 Critical Thinking Questions

1) What am I being asked to believe or accept? 2) What evidence supports this position? 3) Are there other ways this evidence could be interpreted? 4) What other evidence would I need to evaluate these alternatives? 5) What are the most reasonable conclusions?

Mixed-Longitudinal Design

: a method for assessing age-related changes that combines the cross-sectional and longitudinal approaches by observing a cross-section of participants over a shorter period than is sued typically in longitudinal studies. • Participants from a range of ages are observed for a limited period of time, usually about five years. • This approach is faster and less expensive than the longitudinal method and avoids some of the cohort effects of the pure cross-sectional method.

Jane Goodall

A classic example of the method of naturalistic observation is the careful, long-term study of chimpanzees conducted in their habitat by Jane Goodall. In the summer of 1960, the then 26 year-old Goodall began her painstaking observations of chimpanzees living in Tanzania. Among her earlier discoveries was the fact that chimpanzees were not vegetarians, as was previously assumed. As a result of Goodall's years spent following the chimpanzees, scientists have a rich, accurate knowledge of the animals' behavior in the field.

Features that every scientific hypothesis must have

A scientific hypothesis must be both falsifiable and testable

meta-analysis

Conducting a meta-analysis or a statistical analysis of many previous experiments on a single topic (the same topic), often provides a clearer picture than single experiments observed in isolation.

The process of Evaluating Hypotheses

In order to evaluate one's hypothesis, that is based on other's previous findings, the hypotheses must be carefully examined by others in the scientific community through two processes: peer review and replication. -Although this process might slow down the publication of some innovative research, the result - more accuracy - is well worth the effort.

How to find how clustered data is

Look at the Variability through Standard Deviation

Three Measures of Central Tendency

Mean, Median, and Mode

Henry Molaison

One of the most productive case studies in psychology chronicled over 50 years of examinations of Henry Molaison (1926-2008), known in the scientific literature as "the amnesiac patient H.M." In 1953, Molaison underwent brain surgery to control his frequent, severe seizures. Although the surgery may have saved his life, Molaison was left with profound memory deficits. Through painstaking testing and evaluation of Molaison, psychologists learned a great deal about the brain structures and processes that support the formation of memories.

Scatterplot

The way in which to illustrate descriptive statistics using two variables o Each dot represents the intersection between scores on two variables of interest. - the dots are systematically related to each other showing the correlation. o A scatter plot allows us to visualize the relationship between two variables. o We can compute the relationship between the two variables exactly using a correlation coefficient.

How to Illustrate Descriptive Statistics with Two Variables

Use a scatterplot

Falsifiable

a characteristic of a scientific hypothesis meaning that situations in which the hypothesis might be false can be imagined. -this means that you can imagine situations that demonstrate your hypothesis to be false

survey

a descriptive method in which participants are asked the same questions • also known as questionnaires • they allow you to ask large numbers of people questions about attitudes and behavior. • surveys provide a great deal of useful information very quickly at relatively little expense. • one of the primary requirements for a good survey is the use of an appropriate sample

variable

a factor that has a range of values

Testable

a feature of a hypothesis that means it can be evaluated using known scientific methods

experimental group

a group of participants that is exposed to the independent variable

control group

a group that experiences all experimental procedures with the exception of exposure to the independent variable • The experience of the control group should be as similar as possible to that of the experimental groups, who do experience the independent variable

Standard Deviation

a measure of how tightly clustered a group of scores is around their mean. • a smaller standard deviation suggests that most of the scores might be found near the mean. • a larger standard deviation means that the scores are more spread out away from the mean.

correlation

a measure of the direction and strength of the relationship between two variables There are three possible outcomes of correlations between variables: • in positive correlations, high levels of one variable are associated with high levels of another • in negative correlations, high values of one variables are associated with low levels of the other • in zero correlations, the two variables do not have any relationship with each other at all. When variables have a zero correlation, knowing the value of one variable does not tell you anything about the value of the other variable.

dependent variable

a measure that demonstrates the effects of an independent variable; the "result" part of a hypothesis • We use the dependent variable, defined as the observed result of the manipulation of the independent variable, to tell us "that will happen" as a result of the independent variable.

measure

a method for describing variable's quantity It answers the simple question of "how much" of a variable you have observed. o After we obtain measures of each variable, we compare the values of one variable to those of the other and conduct a statistical analysis of the results.

Hypothesis

a proposed explanation for a situation, usually taking the form "if A happens then B will be the result" -it is a type of inference or educated guess based on prior evidence and logical possibilities. o Scientists can never "prove" their hypotheses are true, because some future experiment, possibly using new technology not currently available, might show the hypothesis to be false after all. All we can do is show when a hypothesis is false. o A false hypothesis must always be modified or discarded. o The "proof" of a hypothesis, can be that a hypothesis is proven to be wrong with new information.

Validity

a quality of a measure that leads to valid conclusions (i.e., the measure measures the concept it was designed to measure). o one approach to confirming validity is to see if a measure correlates with other existing, established measures of the same concept.

double-blind procedure

a research design that controls for placebo effects in which neither the participant nor the experimenter observing the participant knows whether the participant was given an active substance or treatment or a placebo

experiment

a research method that tests hypotheses and allows researchers to make conclusions about causality

Statistical Significance

a standard for deciding whether an observed result is due to chance. o To reach conclusions about how our observations fit the big picture, we use inferential statistics. o Recall that in order to prove something, we cannot "prove" a hypothesis to be correct, but we can demonstrate that the hypothesis is false. o We know if a hypothesis should be rejected, psychology has accepted odds of 5 out of 100 or 5% or 0.05 that an observed result is due to chance. Thus, if the chance of something occurring is 0.05 or less, then we can reject the hypothesis.

sample

a subset of a population being studied • good results requires large samples that are typical, or representative, of the population you want to describe. - must mirror the characteristics of the public across factors such as gender, age, education, occupation, income, and geographical location

Normal Distribution

a symmetrical probability function. There are several important features of a normal curve: • it is symmetrical - equal numbers of scores should occur above and below the mean • its shape indicates most of the scores occur near the mean, which is where our measure of variability plays a role • in the standard normal curve, 68% of the population falls within one standard deviation of the mean, 95% falls within two standard deviations of the mean, and 99% of the population falls within three standard deviations of the mean.

Longitudinal Study

an experimental design for assessing age-related changes in which data are obtained from the same individuals at intervals over a long period. • A method that lessens the dilemma of cohort effects is the longitudinal study, in which a group of individuals is observed for a long period. • However, longitudinal studies are difficult to carry out due to the fact that it is expensive and time-consuming to do. Participants drop out of the study due to moves or lack of incentive. Researchers then must worry about whether those who remain in the study will comprise a representative sample.

Cross-sectional study

an experimental design for assessing age-related changes in which data are obtained simultaneously from people of differing ages. • the cross-sectional method introduces what we refer to as cohort effects, or the generational effects of having been born at a particular point in history due to cultural influences of different periods of time.

independent variable

an experimental variable controlled and manipulated by the experimenter; the "if A happens" part of a hypothesis • To test the hypothesis, the researcher manipulates or modifies one or more variables and observes changes in others. The variable controlled an manipulated by an experimenter is known as the independent variable.

case study

an in-depth analysis of the behavior of one person or a small number of people

naturalistic observation

an in-depth study of a phenomenon in its natural setting • naturalistic observation looks at a much larger group of people than a case study, which strengthens our ability to apply the results to the population in general. • gives us the advantage of observing individuals in their natural, everyday circumstances. • this approach has the advantages of providing insight into more natural, real-world behaviors with larger numbers of participants.

placebo

an inactive substance or treatment that cannot be distinguished from a real, active substance or treatment

operationalization

defining variables in practical terms (that are specific). The process of translating abstract independent and dependent variables into concrete forms is called operationalization. • due to the fact that all experimenters must operationalize their variables, they have different definitions of the same variable (Ex. aggression) and thus few comparisons can be made between experiments.

science

o A method for learning about reality through systematic observation and experimentation. o Science, in contrast to faith, absolutely requires proof and evidence. o Science doesn't refer to just any type of knowledge but, rather, to a special way of learning about reality through systematic observation and experimentation.

Summary of Guidelines of Ethical Research on Animal Subjects

o Necessity o Excellent food, housing, veterinary care o Minimal pain and suffering

Summary of Guidelines of Ethical Research on Human Participants

o No coercion o Informed consent o No harm o Confidentiality and privacy

replication

o Unconventional findings often undergo replication: repeating an experiment and producing the same results • During replication, other scientists independently attempt to reproduce the results of the study in question. If the data is replicated, they will be accepted quickly. • If other scientists are unable to replicate the data, their extra effort will have prevented inaccurate results form cluttering the scientific literature.

Correlation Coefficient

o We can compute the relationship between the two variables exactly using a correlation coefficient. o Correlation coefficients can range from +1.00 to -1.00, with a correlation of +1.00 and a correlation of -1.00 being equally strong but differing in the direction of the effect. o A zero correlation indicates the two variables have no systematic relationship at all. o The farther away a correlation coefficient is from zero, the stronger the relationship between the two variables. o When the number of a correlation coefficient is positive, that means we have a positive correlation; when one factor occurs, the other is very likely to occur too. o In a negative correlation, indicate by a correlation coefficient with a minus sign, as one factor increases, the other decreases.

Informed Consent

permission obtained from a research participant after risks and benefits of an experimental procedure have been thoroughly explained.

descriptive methods

research methods designed for making careful, systematic observations o These include case studies, naturalistic observations, and surveys - these provide a good starting place for a new research question. o These methods allow a researcher to make more careful, systematic, real-world observations.

theory

sets of facts and relationships between facts that can explain and predict related phenomena. (they are thoroughly investigated and massively supported principles such as the theory of evolution)

Inferential Statistics

statistical methods that allow experimenters to extend conclusions from samples to larger populations. o Inferential statistics allow us to draw inferences or conclusions from data. o To reach conclusions about how our observations fit the big picture, we use inferential statistics.

Descriptive Statistics

statistical methods that organize data into meaningful patterns and summaries, such as finding the average value. o descriptive data tell us only about the sample we have studied. To determine whether the results from our sample apply to larger populations requires additional methods. o We might approach a mass of data first by asking how the numbers are distributed, then finding various descriptive statistics such as mean, median, and mode in order to gain a better understanding of the values and a frequency distribution.

critical thinking

the ability to think clearly, rationally, and independently. o one of the foundations of scientific reasoning. o the skilled critical thinker can follow logical arguments, identify mistakes in reasoning, prioritize ideas according to their importance, and apply logic to personal attitudes, beliefs, and values. o Critical thinking is not built, but, rather, is a skill that people need to learn.

Reliability

the consistency of a measure, including test-retest, inter-rater, inter-method, and internal consistency. o Test-retest: if you take a test multiple times (ex. if you step on a scale multiple times, your weight should consistently be the same) o Inter-rater: consistency in the interpretation of a measure across different observers o Inter-method: the positive correlation of several approaches to measure a feature in an individual o Internal consistency: results from measures within a single tests that positively correlate with each other.

Median

the halfway mark in a set of data, with half of the scores above and half of the scores below. • The median is far less affected by extreme scores, or outliers, than the mean. Thus, when you have outliers, the median is much more representative of your overall results.

Mode

the most frequently occurring score in a set of data • this is easy to determine from looking at a histogram. • the usefulness of the mode depends on the research question you are asking • using the mode is also an advantage over the use of a mean or median when there is more than one mode in a set of data • ex. the mean age of onset of anorexia is 17 years of age, but the distribution is bimodal - with modes at 14 and 18 years of age.

objectivity

the practice of basing conclusions on fact without influence of personal emotion and bias.

random assignment

the procedure in which each participant has an equal chance of being assigned to any group in an experiment

peer review

the process of having other experts in your area examine and scrutinize research prior to its publication. -Only if other experts conclude that your research is important, accurate, and explained thoroughly will it be added to the existing body of scientific knowledge. -During peer review, research that fits with our existing knowledge is typically accepted more rapidly than work that is less consistent with previous reports

confounding variables

variables that are irrelevant to the hypothesis being tested that can alter a researcher's conclusions. • ex. if some of the participants competed in triathlons without the researcher's knowledge, their athletic experience would confound the interpretation of the results. Random assignment to groups typically controls for confounds due to these types of individual differences, but other sources of confounding exist. • Situational confounds, such as time of day or noise levels in a laboratory, could also affect the interpretation of an experiment.

How to design an experiment (overview)

• A good experimental design features random assignment of participants to groups, appropriate control groups, control of situational variables, and carefully selected independent and dependent variables. • hypothesis & population of interest ⇒ divide into a control group and experimental group through a representative sample of participants and study and test the condition, controlling situational variables • the experimental group receives both the independent and dependent variable • whereas the control group only receives the dependent variable, and does not receive the independent variable

prediction

• the word prediction comes from the Latin words for "saying before." • A prediction is usually stated in a rigorous, mathematical form that allows the scientist to say that under a certain set of circumstances, the following outcomes are likely to occur (if A, then B). (the best scientific theories generate new predictions)