Symptoms of depression and anxiety can significantly impact a patient's health status and quality of life. The APPROACH-IS study administered the Hospital Anxiety and Depression Scale (HADS) to assess the prevalence of depression and anxiety symptoms among adults with congenital heart disease and their potential impact on health status and quality of life. The following table from Kovaks, et al. 2023 publication includes the associated score ranges indicating elevated symptoms of depression and anxiety. Table 1. HADS Score Depression and Anxiety Symptoms 8-10 Mildly elevated 11-13 Moderately elevated 14 or greater Severely elevated Assume the HADS scores in the study sample are normally distributed with a mean of 5.6 and a standard deviation of 4.75. If 19 study participants complete the HADS, what would be the 99% confidence interval around this estimate of the mean?

What is the critical value?

a. 2.552

b. -2.539

c. 2.861

d. 2.878