Question

A patient’s blood volume is often depleted after a major surgery, so a group of researchers designed a drug to increase plasma volume (in ml). They set up an experiment and measured the total circulating volume of blood plasma in a group of patients immediately after they had surgery, and then again one hour after an infusion of the drug into the bloodstream.

Suppose the researchers analyzed the experimental data and got a p-value of 0.13. What would be the appropriate conclusion? (1pt)

List a potential confounding variable for this study and briefly explain a possible impact it might have on the results. (2pt)

Answer 1

In the question, we are testing whether the infusion of the drug increases the plasma volume in the blood of patients who had undergone surgery. Our null hypothesis is that the infusion of the drug has not increased the plasma volume, whereas the alternative hypothesis will be that the drug has increased the plasma volume.

Since the p-value of 0.13 is greater than the 0.05 significance level, we fail to reject the null hypothesis and conclude that there is not enough evidence to support the claim that the infusion of the drug helps in increasing the plasma volume in the patients' blood.

The confounding variable for this study would be the time after which the drug has been infused. We don't know how much time has elapsed between the surgery and the infusion of the drug. If the time elapsed is less, then the plasma level after one hour of infusion of the drug would be substantially higher than if the time elapsed is higher.