Select one of the situations below and answer the following questions: 1. What t

Question

Select one of the situations below and answer the following questions:

1. What threat (or threats) to internal validity might exist in the situation?

2. How could you determine whether the threats you identified actually exist?

Situations:

(a) A researcher decides to try out a new mathematics curriculum in a nearby elementary school and to compare student achievement in math with that of students in another elementary school using the regular curriculum. The researcher is not aware, however, that each of the students in the "new curriculum" school have computers to use in their classrooms.

(b) A researcher wishes to compare two different kinds of textbooks in two high school chemistry classes over a semester. She finds that 20 percent of one group and 10 percent of the other group are absent during the administration of unit tests.

(c) In a study investigating the possible relationship between marital status and perceived social changes during the last five years, men and women interviewers get different reactions from female respondents to the same questions.

(d) Teachers of an experimental English curriculum as well as teachers of the regular curriculum administer both pre- and post-tests to their own students.

(e) A researcher compares the effects of weekly individual and group counseling on the improvement of study habits. Each week, the students counseled as a group fill out questionnaires on their progress at the end of their meetings. The students counseled individually, however, fill out the questionnaires at home.

(f) Those students who score in the bottom 10 percent academically in a school in an economically depressed area are selected for a special program of enrichment. The program includes special games, extra materials, special "snacks," specially colored materials to use, and new books. The students score substantially higher on achievement tests six months after the program is instituted.

(g) A group of elderly people are asked to fill out a questionnaire designed to investigate the possible relationship between "activity level" and "sense of life satisfaction."

Explanation / Answer

(d) Teachers of an experimental English curriculum as well as teachers of the regular curriculum administer both pre- and post-tests to their own students.

The internal validity in an experiment refers to how well an experiment is done. Internal validity in an experiment means how well the cause and effect relationship between the independent variable and dependent variable is carried out, whether the effects on dependent variable is due to the independent variable or was it because of an extraneous variable present. If there are any extraneous variables in an experiment, it results in low internal validity. In the above study, there is no dependent variable. The English curriculum and the regular curriculum is administered on the students, but what effect it has on the students is unknown. This affects the internal validity of the experiment as it is not measuring what it claims to measure. Also, another threat to the internal validity in the above experiment is, it does not include a comparison group. In an experiment, it is of utmost importance to have two groups, control group and experimental group to correlate the scores obtained on both the groups. This helps us understand the cause and effect relationship.

The threats identified indeed exist because an experimental design has to include a comparison group to determine the cause and effect relationship between the independent variable and the dependent variable which wasn't done in the above experiment.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.