Marianne and Leo can't wait to find out whether she is having a boy or a girl. When is the earliest point in her pregnancy when ultrasound imaging will be able to give them an answer?

When moderate levels of stress are associated with optimal performances in testing situation or athletic performances, there is ___________ between the variables.

a. a strong positive correlation b. a curvilinear relation c. no relation a strong negative correlation

In an experimental research design, the variable or condition that is manipulated by the researcher is called the __________ variable

a. independent b. dependent c. subject d. between-group