For each of the following situations, identify the type of threat to internal validity from the list.

a) The researcher tested the effectiveness of a new method of teaching drug dosage and solution calculations to nursing students using a standardized calculation examination at the beginning, midpoint, and end of a 2-week course.
b) In a study of the results of a hypertension teaching program conducted at a senior center, the blood pressures taken by volunteers using their personal equipment were compared before and after the program.
c) The smoking cessation rates of an experimental group consisting of volunteers for a smoking cessation program were compared with the results of a control group of people who wanted to quit on their own without a special program.
d) Thirty percent of the subjects dropped out of an experimental study of the effect of a job- training program on employment for homeless women. Over 90% of the dropouts were single homeless women with at least two preschool children, whereas the majority of subjects successfully completing the program had no preschool children.

A. Selection bias
B. Mortality
C. Testing
D. Instrumentation

a) The researcher tested the effectiveness of a new method of teaching drug dosage and solution calculations to nursing students using a standardized calculation examination at the beginning, midpoint, and end of a 2-week course. - MATURATION.

b) In a study of the results of a hypertension teaching program conducted at a senior center, the blood pressures taken by volunteers using their personal equipment were compared before and after the program. - INSTRUMENTATION.

c) The smoking cessation rates of an experimental group consisting of volunteers for a smoking cessation program were compared with the results of a control group of people who wanted to quit on their own without a special program. - SELECTION BIAS.

d) Thirty percent of the subjects dropped out of an experimental study of the effect of a job- training program on employment for homeless women. Over 90% of the dropouts were single homeless women with at least two preschool children, whereas the majority of subjects successfully completing the program had no preschool children. - MORTALITY

the correct answer is ) possibility.

demonstrating opportunity cost is done through production possibility.

the opportunity cost can be demonstrated using the production possibility frontier or curve. this graphic shows the total number of possibilities for two products when we have the resources needed and used in an efficient manner. the main resources could be money, labor, and technology. the curve shows that the production of one good increases when the production of the othe

thomas jefferson

explanation: