Question

For each of the following cases \([(a)\) and \((b)]\), (I) state whether the study should be observational or experimental. (II) state whether the study should be run blind, doubleblind, or neither. If the study should be run blind or double-blind, who should be blinded? (a) An investigation of whether the size of the midsagittal plane of the anterior commissure (a part of the brain) of a man is related to the sexual orientation of the man. (b) An investigation of whether drinking more than 1 liter of water per day helps with weight loss for people who are trying to lose weight.

Short answer

Case (a) should be observational, no blinding necessary but researcher may be blinded. Case (b) should be experimental, conducted as double-blind with both participants and researchers blinded.

Step-by-step solution

Part (a) - Observational or Experimental

For case (a), since the trait (size of the midsagittal plane of the anterior commissure) is a natural characteristic that cannot be controlled or manipulated by the researcher, the study would be observational. Researchers simply observe and measure characteristics without affecting them.

Part (a) - Blinding in the Study

For the observational study in case (a), blinding is not typically necessary as the data involves physical measurements that do not change based on participant or researcher expectation. However, to avoid bias in measuring or interpreting the data, the researcher could be blinded from the participant's sexual orientation.

Part (b) - Observational or Experimental

For case (b), the study should be experimental because the researcher is interested in the effects of a controlled intervention (drinking more than 1 liter of water per day) on a specific outcome (weight loss). Participants can be assigned to different conditions to compare the outcomes.

Part (b) - Blinding in the Study

In the experimental study of case (b), it should be run double-blind to prevent both participant and researcher biases. The participants should be blinded to whether they are in the control group or the treatment group, and the researchers should be blinded to which group the participants are in when assessing the outcome to prevent biased interpretation of results.

Key concepts

Blinding in Research

Blinding is a technique used in research studies to reduce bias. In studies where behavior or perceptions can influence the outcomes, blinding is essential to maintain the integrity of the results. It involves concealing certain information from participants or researchers to prevent their knowledge from affecting study behaviors or interpretations.

In case (b) 'An investigation of whether drinking more than 1 liter of water per day helps with weight loss', a double-blind study is recommended. This entails that neither the participants nor the researchers know who belongs to the control group or the treatment group until the conclusion of the study. Blinding the participants helps prevent placebo effects or changes in behavior due to knowing they are receiving a special treatment. Blinding the researchers prevents them from subconsciously influencing participants or interpreting data with prejudice. Thus, blinding is crucial in experimental studies for achieving unbiased and reliable results.

Research Bias

Research bias refers to systematic errors that distort the findings of a study. Bias can arise from multiple sources throughout the stages of research, including in the design, data collection, analysis, and reporting phases. Some common types of bias include selection bias, information bias, and confirmation bias.

To mitigate these biases, in case (a) 'An investigation of the size of the anterior commissure in relation to sexual orientation', where the study is observational, it is acknowledged that while blinding might not be typical, it is beneficial to blind researchers from knowing the participants' sexual orientation to prevent unintended influence when measuring or interpreting the brain scans. This action demonstrates an awareness of the potential for bias even in observational research and an effort to maintain objectivity.

Control Group

In experimental studies, the control group consists of participants who do not receive the experimental treatment or intervention being tested. This group serves as a baseline to compare the changes or effects observed in the treatment group, providing a clear picture of whether the treatment had any genuine effect.

The necessity of a control group is emphasized in experimental study (b), where participants not drinking more than 1 liter of water per day would make up the control group. They enable us to see if any weight loss in the treatment group exceeds normal fluctuations that occur without the increased water intake. Assigning a control group helps control for external variables, thus improving the study's validity.

Treatment Group

The treatment group, on the other hand, comprises participants who receive the experimental treatment or intervention. In case (b), this group would be the individuals who drink more than 1 liter of water per day. The treatment group is pivotal in determining the effectiveness of the intervention. By comparing the results between the treatment and control groups, researchers can analyze the impact of the intervention while accounting for other variables.

When the treatment group shows significantly different outcomes than the control group, and the study is properly blinded and randomized, one can infer that the treatment is likely the cause of the difference.