I. The Experiment MethodA. Definition○ An experiment is a carefully controlled method of investigation used to establish cause-and-effect relationship by manipulating selected variables in order to determine cause and effect.B. Testable Hypothesis○ A hypothesis is a tentative statement that describes the relationship between two or more variables. It must be testable, verifiable, and refutable.○ Independent Variable - the factor that is manipulated or controlled by the experimenter.○ Dependent Variable - is the factor that is measured by the experimenter. It is affected by and thus dependent on the independent variable.○ The hypothesis must have an operational definition - is a precise description of how the variable in a study will be manipulated and measured.C. Participants: Experimental and Control Groups○ The experimental group comprises the participants who are exposed to the independent variable.○ The control group comprises the participants who are exposed to all experimental conditions except the independent variable. This allows for comparisons with the experimental group.○ Confounding Variables - in a controlled experiment, an unwanted influence between the experimental group and the control group other than the independent variable that can alter the resultsD. Experiment Controls○ Purpose - controls are used to ensure all groups in the experiment are treated exactly the same○ Problems - experimenter bias can occur and so can sample bias if subjects aren’t representing the larger population○ Solutions - random assignment, placebo, single-blind study, double-blind studyE. Advantages of Experiments○ Identify cause-and-effect relationships○ Distinguish between real and placebo effects○ Control bias by using a double-blind study○ Manipulate the independent variable and measure the dependent variables○ Replicate a study, increasing the confidence that the independent variable influences the dependent variables.F. Disadvantage of Experiments○ Create artificial lab conditions that may not always correspond to real-life situations○ Can be compromised by confounding variables that are difficult to identify and control○ Susceptible to researcher and participant biases.○ Raise ethical concerns when subjects are deceivedII. Descriptive ResearchIt includes methods that enable researchers to observe and describe behaviors and mental processes without manipulating variables. Descriptive methods do not enable researchers to establish cause-and-effect relationships.A. Surveys○ A research technique that uses questionnaires or interviews or a combination of the two to assess the behavior, attitudes, and opinions of a large number of people.○ The entire group a researcher studies is a population.○ Usually only a sample of the population is used and a random sample, where everyone has a chance of participating, minimizes bias and ensures the sample is representative.○ Social desirability bias - survey respondents often report they are healthier and happier than in other types of researchers.B. Naturalistic ObservationWhen the researchers observe the behavior of subjects in a real social setting○ It is very revealing, but they are descriptive and do not explain behaviorC. Case StudiesAn in-depth examination of a single research participant.○ Researchers can obtain detail knowledge about a person and offer the opportunity to conduct studies of rare and unusual cases.○ They cannot be used to establish cause-and-effect relationships. They are susceptible to inaccurate reporting and the subject’s biased views.D. Studies of Development○ Longitudinal method measures a single individual or group over an extended period of time. They are expensive and time consuming.○ Cross-sectional method compares individuals of various ages at one point in time. They can provide information about age differences, but it’s very difficult to make generalizations since they measure behavior at only one point in time.III. Correlation StudiesA. Definition○ A relationship between variables in which changes in one variable are reflected in changes in the other variable. Variables are not directly manipulated.○ Correlations can be used to analyze the data gathered in any type of descriptive method.B. Correlation ○ A numerical value that indicates the strength and direction of the relationship between two variables.○ Calculated by a formula that produces a number ranging from +1.00 to -1.00.○ Positive correlation - two variables move in the same direction○ Negative correlation - two variables move in opposite directions○ Zero correlation - when there is no relationship between variablesC. Correlation and Causation○ Correlation studies indicate the possibility of cause-and-effect relationship. Remember correlation does not prove causeD. Advantages of Correlation Studies○ Describe or clarify a relationship between two variables○ Efficient way to utilize preexisting data○ Dispel illusory correlations, such as an assumed correlation between birthday and personality traits.E. Disadvantages of Correlation Studies○ Cannot establish cause-and-effect relationships○ Cannot establish the direction of causal influence○ Doesn’t allow researchers to actively manipulate the variables.○ Makes it difficult to identify the impact of confounding variables.IV. Descriptive StatisticsA. Measures of Central Tendency○ Mean - is the average score of all data○ Median - the score that divides a frequency distribution exactly in half, so that the same number of scores lies on each side of it.○ Mode - the most frequently occurring score in a distribution.B. Measures of Variation○ Range: the highest score in a distribution minus the lowest score○ Standard deviation: the most widely used measure of variation and the standard measurement of how much the scores in a distribution deviate from the mean. (distance from the mean -/+)○ Normal distribution: form a bell-shaped curve○ In a normal distribution of test scores, the percentage of scores that fall at or above the mean score is 50.○ The percentage of test scores that fall at or below that mean score is also 50.○ In a normal distribution, ⅓ of the scores fall one standard deviation below the mean and ⅓ fall one standard deviation above the mean.○ C. Skewed Distributions: contains a higher number of scores on the low end of the scale.○ Negatively skewed distributions: contains a