Final answer:
The lowest concurrent validity, indicated by the correlation coefficient, is -1, which reflects a perfect negative correlation between the measures.
Step-by-step explanation:
The question pertains to the concept of concurrent validity, which is a measure of how well a particular test correlates with a previously validated measure. Concurrent validity can be determined by looking at the correlation coefficient between the two measures, which can range from -1 to +1. A correlation coefficient of +1 indicates a perfect positive correlation, while -1 indicates a perfect negative correlation. A correlation of 0 implies no relationship between the two measures. Considering that the question asks for the lowest concurrent validity, we would look for the lowest possible correlation coefficient, which is -1.