(c) the variable age is a possible confounder...
(c) the variable age is a possible confounder in this study. choose the best reason why.\n\na variable is a confounder if its effect on the outcome cannot be distinguished from the effect on the outcome from different treatments. (in our context, the outcome is bone density, and the treatments are has/had cancer and never had cancer.) there is already a noticeable difference between the two groups of participants in terms of having cancer. its possible the participants in the hc group differ from the participants in the nhc group in other characteristics, such as age, making it difficult to determine which variable is affecting bone density.\n\na variable is a confounder if, based on its value, it prohibits some members of the sample from participating in the study. for this study, there may be some people in the sample who have a birthday during the study. thus, their age would change during the study making it not possible for them to participate.
Answer
# Brief Explanations:
A confounder is a variable whose effect on the outcome cannot be separated from the effect of the treatment. Age may differ between the cancer - having (HC) and non - cancer - having (NHC) groups and affect bone density, making it hard to isolate the effect of cancer on bone density. The second option about age changing during the study and preventing participation is not the correct definition of a confounder.
# Answer:
A. A variable is a confounder if its effect on the outcome cannot be distinguished from the effect on the outcome from different treatments. (In our context, the outcome is bone density, and the treatments are has/had cancer and never had cancer.) There is already a noticeable difference between the two groups of participants in terms of having cancer. It's possible the participants in the HC group differ from the participants in the NHC group in other characteristics, such as age, making it difficult to determine which variable is affecting bone density.