L7 Reality check

State True or False. All experimental studies are analytical studies.

State True or False. Systematic errors arise because of the way the research is designed in such a way that one answer is preferred over another.

In a research study, the researchers wanted to study the impact of a certain type of knee exercise (as part of physiotherapy) on the time taken to return to work involving lot of walking. They compared the outcomes in people who could perform the knee exercise with the outcomes in people who could not perform the knee exercise because of their pain. They found that the people who performed physiotherapy returned to work earlier. What is the type of bias in the above study?

State True or False. It may be difficult to distinguish whether the variable is a confounding variable or a mediator variable in some study designs.

State True or False. A researcher wants to find out whether surgery is better than active surveillance in localised prostate cancer. They included only people without any major comorbidities in each groups. This can result in selection bias as they have included only certain type of men and not all men in whom a decision about treatment has to be made.

A researcher wants to find the association between cancer and consumption of sugary fizzy drinks. They identify people with cancer and similar type of people without cancer and ask such people about the quantity of sugary fizzy drinks that they consumed in the last 30 years. What type of bias does this lead to?

A researcher wants to find out whether physiotherapy is better than no physiotherapy after knee arthroscopy. Let us say that the researchers ensured that similar type of people received physiotherapy and no physiotherapy. The physiotherapy visit was arranged one week after surgery. While the main aim was physiotherapy, the physiotherapist identifies any painful swelling in the knee during the visit and refers the patients for further investigations and treatment. On the other hand, the patients who did not undergo physiotherapy were seen by their general practitioner (GP) 2 weeks after the surgery and referred for further investigations and treatment. If the main aim of the study was whether physiotherapy was better and not whether healthcare professional review at 1 week after surgery is better than healthcare professional review at 2 weeks or whether review by a physiotherapist is better than GP review, what type of bias does this result in?

A researcher wants to find out whether starting nutritional counselling (twice a week for 4 weeks) before surgery decreases surgical complications compared to no nutritional counselling. They ensure that similar type of people receive nutritional counselling and no nutritional counselling. They excluded participants who did not at least 80% of the nutritional counselling sessions. What type of bias does this result in?

A researcher wants to find out whether an exercise fitness regimen is useful in decreasing weight in overweight people. They ensure that similar type of people receive the exercise fitness regimen and no exercise fitness regimen. In people who underwent exercise fitness regimen, the weight was measured using an accurate weighing machine. People who did not undergo exercise fitness regimen were asked to measure their own weights at home. What type of bias does this result in?

A researcher wants to find out whether cardiac-output guided fluid therapy (i.e., you measure the blood that the heart pumps out in some way; this is called 'goal-directed fluid therapy') is better than standard fluid therapy (determined by urinary output and estimated daily fluid losses) in decreasing complications after major emergency abdominal surgery. They measure 10 different surgical complications and report the complications that are different statistically between the two groups. What type of bias does this result in?