# Validity in Quantitative Research Designs

Reflect on the following scenarios:

Wanda has been involved in a research study of the causes of tooth decay in elementary school children. Twenty-five percent of the students in the free breakfast program at a local school have been screened by a local dental hygienist. The dental hygienist finds an average of 3.5 cavities per student. The same dental hygienist recently screened 25% of the students in a school with no free breakfast program, and found an average of only 1.5 cavities per student. Wanda concludes that the breakfast served to students is the cause of higher tooth decay. Do you agree with Wanda? Can you think of other causes for the higher number of cavities among the students from the school with free breakfast?

Jerry is conducting a phone survey to determine public opinions on Medicaid reform. In order to get a random sample, Jerry decides to call the tenth number on the second column of every fifth page of the phone book. He also decides to stop sampling when he has completed 50 surveys. After reaching the target number, Jerry begins to analyze the data he has gathered and is surprised to find that opposition to reform is running about 18% higher than the national average. He is at a quandary to explain this significant difference in numbers. What are some reasons you can think of for the higher rate of opposition?

As you consider these scenarios, you may note issues or problems related to the validity of the research and conclusions. This week, you assess validity in quantitative research. You are introduced to the different types of validity and why they are important to consider when evaluating evidence and research studies. You also examine common threats to validity and consider how to minimize those threats.

Discussion: Validity in Quantitative Research Designs

Validity in research refers to the extent researchers can be confident that the cause and effect they identify in their research are in fact causal relationships. If there is low validity in a study, it usually means that the research design is flawed and the results will be of little or no value. Four different aspects of validity should be considered when reviewing a research design: statistical conclusion validity, internal validity, construct validity, and external validity. In this Discussion, you consider the importance of each of these aspects in judging the validity of quantitative research.

To prepare:

• Review the information in Chapter 10 of the course text on rigor and validity.
• Read the method section of one of the following quasi-experimental studies (also located in this week’s Learning Resources). Identify at least one potential concern that could be raised about the study’s internal validity.
• Metheny, N. A., Davis-Jackson, J., & Stewart, B. J. (2010). Effectiveness of an aspiration risk-reduction protocol. Nursing Research, 59(1), 18–25.
• Padula, C. A., Hughes, C., & Baumhover, L. (2009). Impact of a nurse-driven mobility protocol on functional decline in hospitalized older adults. Journal of Nursing Care Quality, 24(4), 325–331.
• Yuan, S., Chou, M., Hwu, L., Chang, Y., Hsu, W., & Kuo, H. (2009). An intervention program to promote health-related physical fitness in nurses. Journal of Clinical Nursing, 18(10), 1,404–1,411.
• Consider strategies that could be used to strengthen the study’s internal validity and how this would impact the three other types of validity.
• Think about the consequences of an advanced practice nurse neglecting to consider the validity of a research study when reviewing the research for potential use in developing an evidence-based practice.

Post the title of the study that you selected and your analysis of the potential concerns that could be raised about the study’s internal validity. Propose recommendations to strengthen the internal validity and assess the effect your changes could have with regard to the other three types of validity. Discuss the dangers of failing to consider the validity of a research study