When the relationship between a test and performance is low in a concurrent study, one likely reason may be:

Restriction of range  

Explanation:

In concurrent study, the test is administered and the criteria is being measured at relatively about the same possible time.  

The test results may not correlate with the performance data because there may be a restriction of the range occurrence.

This is the main reason for the low relationship between the performance and test.

So, the correct answer is " Restriction of range".

1. seasonal

2. frictional unenployment

3. the number of the labor force multiplied by 100 and then subtract the number of unemployed.

4. 4%

5. an increase in prices