Answer to Question 1
By assigning participants to groups on the basis of the flip of a coin, numbers drawn from a hat, or a table of random numbers, the chance is increased that characteristics other than the independent variable will be equally distributed across treatment groups.
Answer to Question 2
The rate and expression of childhood symptoms and disorders often vary in relation to demographic and situational factors, such as socioeconomic status (SES) (e.g., the social, economic, and physical environment in which the child lives as reflected in measures such as family income, education, or occupation); parents' marital status; and the child's age, gender, and cultural background, to name but a few. Consequently, these variables must be assessed and controlled in most studies.
In countries where water can be contaminated, breastfeeding is an important option for the health of ...
A typical variable cam timing control valve. The solenoid is controlled by the engine computer and ...
Hydrolysis reactions for some biochemically important phosphate compounds (part 2)
Nutrition-related research findings are often lead stories in newspapers, magazines, and on websites
Researchers and Research Spending, 2009
Gel electrophoresis, an essential laboratory technique in biological science research