A researcher is performing a study of post-menopausal estrogen users and endometrial cancer and recruiting participants only from hospitalized patients. This type of recruitment may result in:

In this scenario, the recruitment of participants exclusively from hospitalized patients can lead to selection bias. This occurs because the population of hospitalized individuals is not representative of the general population of post-menopausal estrogen users. For instance, these patients may have more severe health issues or different socio-economic backgrounds compared to those who are not hospitalized. As a result, their experiences and health outcomes related to endometrial cancer may not accurately reflect those of the broader community of post-menopausal estrogen users.

Selection bias can skew the results of the study, making it difficult to generalize the findings. When research conclusions are drawn from a non-representative sample, it raises questions about the validity and applicability of the study's findings to other groups.

Other options, such as confounding factor and misclassification bias, pertain to different issues in research methodology and are not as directly related to the specific recruitment process discussed in this case. ANOVA, a statistical method, does not pertain to selection issues at all. Thus, the significant concern here focuses on how the method of participant recruitment could distort the study's results, leading to the identification of selection bias as the correct answer.