study and control groups

Method- The   purpose and population for the investigation
1. Study hypothesis
What is the study question being investigated?

2. Study   population
What   population is being investigated and what are the inclusion and exclusion   criteria for the participants of the investigation?

3. Sample size and statistical power
How many individuals are included in the study and in   the control groups? Are the numbers adequate to demonstrate statistical   significance if the study hypothesis is true (what is the statistical power)?


Assignment-   Selection of participants for the study and control groups
1. Process
What method is used to identify and assign individuals or populations to study  and control groups?

2. Confounding variables
Are there differences between study and control groups, other than the factor   being investigated, that may affect the outcome of the investigation?

3. Masking or blinding
Are the participants and/or the investigators aware of the participants’   assignment to a particular study or control group?


Assessment- Measurement of   outcomes or endpoints in the study and control groups
1. Appropriate
Does the measurement of   outcomes address the study’s question?

2. Accurate and   precise
Is the measurement of   outcomes an accurate and precise measure of the phenomenon that the   investigators seek to assess?

3. Complete and unaffected by observation
Is the outcome measurement   nearly 100% complete and is it affected by the participants’ or the   investigators’ knowledge of the study group or control group assignment?


Results-   Comparison of outcomes in the study and control groups
1. Estimation
What is the magnitude or   strength of the relationship observed in the investigation?

2. Inference
What statistical   technique(s) are used to perform statistical significance testing?

3. Adjustment
What statistical technique(s) are used to take into   account or control for differences between the study group and the control   group that may affect the results?


Interpretation-   Meaning of the results for those included in the investigation
1. Contributory cause   or efficacy
Does the factor being investigated alter the   probability that the disease will occur (contributory cause) or work to   reduce the probability of undesirable outcomes (efficacy)?


2. Harms
Are adverse events that affect the meaning of the   results identified?

3. Subgroups and interactions
Do the outcomes in subgroups differ and are there   interactions between factors that affect outcomes?


Extrapolation- Meaning for those not specifically included   in the investigation
1. To similar individuals, groups, or populations
Do the   investigators extrapolate or extend the conclusions to individuals, groups,   or populations that are similar to those who participated in the   investigation?

2. Beyond the data
Do the investigators extrapolate by extending the   conclusions beyond the dose, duration, or other characteristics of the   investigation?

3. To other populations
Do the investigators extrapolate to populations or   settings that are quite different from those in the investigation?

Rev. 2021

Riegelman, R.K. & Nelson, B.A. (2021). Studying a study & testing a test. Wolters Kluwer.

Bovbjerg, M. L., Cheyney, M., & Everson, C. (January 01, 2016). Maternal and Newborn Outcomes Following Waterbirth: The Midwives Alliance of North America Statistics Project, 2004 to 2009 Cohort. Journal of Midwifery & Women’s Health, 61, 1, 11-20.

Links to an external site.

Bovbjerg_et_al-2016-Journal_of_Midwifery_%26_Women-s_Health.pdf (attached)

study and control groups


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