Research Methods

Unit 2 (Chapter 2)

The Scientific Approach

• Empiricism• Basic assumption: events are governed by

some lawful order• Goals:

• Measurement and description• Understanding and prediction• Application and control

• Goal of theory testing in science: refutation not proving

• 1. Developing a Hypothesis:-Hypothesis: A statement predicting

the outcome of a scientific study or describing the relationship among variables in a study.

• 2. Design test: A hypothesis must undergo rigorous tests before it will be accepted as a legitimate theory.

• To make a test controlled, one must account for the independent variable. • Independent Variable: A stimulus

condition that the experimenter changes independently of all other carefully controlled conditions in the experiment.

• 3. Collect data: getting information by direct observation that relies only on the independent variable and not on the experimenter’s hopes. This data is called the dependent variable.

• Dependent Variable: The measured outcome of a study, or the response of the subjects in the study.

• 4. Analyzing the results: This step consists of looking at the data collected and seeing if it supports or disproves the hypothesis.

• 5. Publishing, criticizing and replicating the results: The last step of the scientific method is to have the results withstand the criticism and scrutiny of the science community.

• Replicate: To do a study over to see if the same results are obtained. To control for bias, the replication is most often done by someone other than the original researcher.

The Scientific Method: Terminology

• Operational definitions are used to clarify precisely what is meant by each variable

• Participants or subjects are the organisms whose behavior is systematically observed in a study

• Data collection techniques allow for empirical observation and measurement

The Scientific Method: Terminology

• Statistics are used to analyze data and decide whether hypotheses were supported

• Findings are shared through reports at scientific meetings and in scientific journals – periodicals that publish technical and scholarly material• Advantages of the scientific method: clarity

of communication and relative intolerance of error

• Research methods: general strategies for conducting scientific studies

Experimental Research: Looking for Causes

• Experiment = manipulation of one variable under controlled conditions so that resulting changes in another variable can be observed• Detection of cause-and-effect relationships

• Independent variable (IV) = variable manipulated

• Dependent variable (DV) = variable affected by manipulation • How does X affect Y? • X= Independent Variable, and Y=

Dependent Variable

Experimental and Control Groups

• Experimental group – subjects who receive some special treatment in regard to the independent variable

• Control group – similar subjects who do not receive the special treatment• Logic:

• Two groups alike in all respects (random assignment)

• Manipulate independent variable for one group only

• Resulting differences in the two groups must be due to the independent variable

• Extraneous and confounding variables

Experimental Designs: Variations

• Expose a single group to two different conditions• Reduces extraneous variables

• Manipulate more than one independent variable• Allows for study of interactions between

variables• Use more than one dependent variable

• Obtains a more complete picture of effect of the independent variable

Descriptive Research Methods

• Strategies for observing and describing behavior

• Typically words instead of numbers (qualitative)

• Do not manipulate anything in the research

Observations

• Observe behavior by watching and recording information• Naturalistic – in the natural setting,

creates a purer result• Lab – more controlled, but less

natural

Case Studies

• One individual studied in great detail• Typically rare cases

• You collect information in several ways

Surveys

• Asking questions about a specific topic• Very direct• Use interviews, questionnaires, surveys

Statistics and Research

• Statistics – using mathematics to organize, summarize, and interpret numerical data

• Descriptive statistics: organizing and summarizing data

• Inferential statistics: interpreting data and drawing conclusions – use of probability

Descriptive Statistics: Measures of Central Tendency

• Measures of central tendency = typical or average score in a distribution

• Mean: arithmetic average of scores• Median: score falling in the exact center• Mode: most frequently occurring score

• Which most accurately depicts the typical?

Descriptive Statistics: Variability

• Variability = how much scores vary from each other and from the mean• Standard deviation = numerical depiction

of variability• High variability in data set = high

standard deviation• Low variability in data set = low standard

deviation

Normal Distribution

A standard deviation of 1 accounts for about 68% of responses.

A normal distribution is a bell shaped curve.

Descriptive Statistics: Correlation

• When two variables are related to each other, they are correlated.

• Correlation = numerical index of degree of relationship• Correlation expressed as a number

between 0 and 1• Can be positive or negative• Numbers closer to 1 (+ or -) indicate

stronger relationship

Figure 2.13 Positive and negative correlation

Which of the following correlation coefficients presents the strongest relationship betweenthe variables?a. .02b. -.67c. .55d. -.14

Correlation: Prediction, Not Causation

• Higher correlation coefficients = increased ability to predict one variable based on the other• SAT/ACT scores moderately correlated with

first year college GPA • 2 variables may be highly correlated, but not

causally related• Foot size and vocabulary positively correlated• Do larger feet cause larger vocabularies?• The third variable problem

Inferential Statistics: Interpreting Data and Drawing Conclusions

• Hypothesis testing: do observed findings support the hypotheses? • Are findings real or due to chance?

• Statistical significance = when the probability that the observed findings are due to chance is very low• Very low = less than 5 chances in 100/ .05

level• Other factors might account for the results

Sampling

• Representative Sample: A sample obtained in such a way that it reflects the distribution of important variables in the larger population in which the researcher are interested-variables such as age, SES, ethnicity, education….

Evaluating Research: Methodological Pitfalls

• Sampling bias • Placebo effects – is not always uniform –

cost factors and perceived pain• Distortions in self-report data:

• Social desirability bias • Response set

• Experimenter bias • the double-blind solution• Research protocol of clinical trial for drugs –

FDA in U.S.

Internet Psychological Research

Internet-mediated research refers to studies in which data collection occurs over the web.

Possible Advantages• Samples that are much larger and much

more diverse than the samples used in lab research

• Have the potential to yield more diverse and representative samples

Internet Psychological Research

Potential Disadvantages• Sampling bias resulting from self-selection

may be a more troublesome issue in Internet-mediated research• Web users tend to be younger, brighter,

and more affluent than nonusers• Data are collected under far less controlled

conditions than in traditional studies

Ethics in Psychological Research: Do the Ends Justify the Means?

• The question of deception• The question of animal research

• Controversy among psychologists and the public

• Ethical standards for research: the American Psychological Association• Ensures both human and animal subjects

are treated with dignity

Ethics in Psychological Research: Do the Ends Justify the Means?

• Tuskegee Syphilis Study:• http://www.cdc.gov/tuskegee/timeline.htm