Elsa is doing clinical research about PTSD treatments. To measure the severity of her patients' initial symptoms, she decides to use a questionnaire that other researchers have been using for many years. Based on what she read about the thousands of other PTSD patients who have taken this questionnaire in previous studies, = 74. In Elsa's study, 90 participants take this questionnaire, and she found a sample mean of 70. What do these two values tell us (in the context of this example)? Is it concerning that the two values are not identical, or is that something we would expect to see?