Final answer:
The T-test for agility does not have good external validity for sports with complex movement patterns due to the high uncertainty in measurement, affecting its ability to predict actual sports performance accurately.
Step-by-step explanation:
The statement that the T-test for agility does not have good external validity for sports that include multiple movement patterns is true. External validity refers to the extent to which the results of a study can be generalized to other situations and to other people. When considering the effectiveness of a strength development class in making players stronger, one must look at whether the results of any test used apply to real-world scenarios, in this case, sports that involve complex, multiple movement patterns.
In the context of the T-test for agility, factors such as the uncertainty in the stopwatch can greatly affect the ability to measure improvements accurately. If the uncertainty is too significant, it impairs the ability to detect small but meaningful differences in performance, thereby reducing the applicability of the test's results to actual sports performance. This suggests that the test might not effectively predict or reflect improvements in agility that would translate into better sports performance for athletes who participate in sports with various complex movements.