Addiction

What is a Simple Random Sample?

Description: Each member of the population has an equal chance of being selected.
Advantages: For very large samples, this gives the best chance of an unbiased or representative sample.
Disadvantages: For large populations, this is time-consuming. It is hard to truly get a random sample, because participants with computers or landline phones may be more likely to be selected.

What is a Stratified Random Sample?

Description: The population is divided into subcategories such as age, gender, and race, and members are selected in the proportion that they occur in the population.
Advantages: Representative sample. Can be generalized to the general population.
Disadvantages: Time-consuming. Subcategories have to be identified and their proportions calculated.

What is a Purposive Sample?

Description: Investigator purposely chooses participants based on certain characteristics.
Advantages: Economical and less time-consuming. Can focus on subjects with relevant characteristics.
Disadvantages: Selection bias can threaten external and internal validity.

What is a Self-selection/Volunteer Sample?

Description: People self-select to participate—those who respond to an ad or show up for a study.
Advantages: Convenient, quick, and economical.
Disadvantages: Nonrepresentative. Volunteer bias can threaten external validity and internal validity, because differences in participants may underlie results.

CT scans

computerized axial tomography uses a series of X-ray beams that rotate around the head and are passed through the skull, creating a cross-sectional image of the brain. Provide a three-dimensional image and helpful in evaluating many structural problems of the brain, such as tumors or trauma

MRI

uses strong magnetic fields loudly to distinguish different body tissues based on their water content. produce higher-contrast images of soft tissues and they cannot be used in patients with metallic devices, and they need to lie still in a tight, enclosed space.

EEG

record the electrical activity of the brain for Action potentials and electrodes record this activity. assess states of consciousness.

PET

measuring the brain’s metabolic activity. A patient is injected with a radioactive substance called 2-deoxyglucose (2-DG), which resembles glucose and when 2-DG decays, it emits subatomic particles called positrons. Produces a colored picture of that section of the brain, provide functional, not just anatomical, information about the brain.

fMRI

provides both an anatomical and functional view of the brain by detecting levels of oxygen in the brain’s blood vessels. Has a higher resolution, is noninvasive, and does not use a radioactive tracer. Its accuracy, questionable