A t-test is most appropriate when only analyzing two variables. Dr. Crawford is analyzing the means produced by students in Group C, but under two different conditions. This test will determine whether the differences in means is due to chance or if there is a statistically sound significant difference.

A normal distribution is asymptotic because it approaches a curve closely. It is unimodal because of its singular mode, and it is symmetric because both sides are mirror images of each other. There are other kinds of distributions like skewed distributions that are unimodal, asymptotic, and asymmetrical. These descriptions can vary depending on the shape of the distribution. 

An hypothesis is a conclusion drawn before all of the facts are established and tentatively accepted as a basis for further investigation.

A conclusion is the final operation in the scientific method. It is a decision made about the validity of the hypothesis on the basis of experimental evidence. Observation is the first operation in the scientific method. Observation is the noting of a specific phenomenon leading to the formulation of a hypothesis. Perception is the organization, identification, and interpretation of sensory information. An assumption is an idea that is not subjected to logical study. 

In an experiment, the dependent variable is changed by changes to the independent variable; because this study examines how differences in smoking habits affect blood pressure, the number/frequency of cigarettes smoked is the study's independent variable and the subjects' blood pressure is the study's dependent variable.

Sequential cohort studies are a combination of longitudinal and cross-sectional methods insofar as they compare the behaviors or attitudes of specific groups of people over an extended time period.

Correlations explain the strength and direction of the relationship between two variables; however, these relationships do not indicate direct causality. For instance, the relationship can be caused by a third variable, called a confounding variable. Correlations—no matter how strong—do not imply causation.

Modern IRBs have set standards for the ethical treatment of subjects. Each of the studies listed violated the regulations set by IRBs. Milgram’s use of deception violated the rights of his subjects and may have exposed them to unnecessary mental anguish. Zimbardo’s prison experiment was not terminated after “prison guards” inhumanely abused “inmates,” which resulted in both physical and mental harm of subject’s well being. Last, researchers in the Tuskegee Syphilis Experiment did not provide treatments to subjects in order to observe the final stages of the disease, which resulted in the death and suffering of many individuals. Each of these violated the rights of subjects involved in varying degrees.

Modern IRBs have set standards for the ethical treatment of subjects. Each of the studies listed violated the regulations set by IRBs. Milgram’s use of deception violated the rights of his subjects and may have exposed them to unnecessary mental anguish. Zimbardo’s prison experiment was not terminated after “prison guards” inhumanely abused “inmates,” which resulted in both physical and mental harm of subject’s well being. Last, researchers in the Tuskegee Syphilis Experiment did not provide treatments to subjects in order to observe the final stages of the disease, which resulted in the death and suffering of many individuals. Each of these violated the rights of subjects involved in varying degrees.