Jared is conducting an experiment with extrasensory perception (ESP) training. He begins with a pretest of his 40 participants and then divides them into two groups based on their scores. The participants with the 10 lowest scores are given extensive training on how to detect the signals. The participants with the 30 highest scores are given no training. Both groups are retested and the average score of the participants with the training improved, whereas the average score of the participants without the training fell. Which threat to internal validity should Jared consider?

regression threat

Explanation:

Internal validity is a measure of how the conditions of an experiment makes a difference and whether there is enough evidence to come to a vivid conclusion. There are several threats to internal validity, which include, history, testing, instrumentation, subject selection, selection maturity, and regression. Regression threat is also called regression to the mean. The main cause of this threat is selecting subjects based on extreme scores or characteristics, as the case may be in the example. Jared selected participants with extreme scores.

where's the

stable food supply,social structure, government,religion,culture/art,technology and writing/language;