The skill of common bird in daily Task has been studied, and some results are opposite of expectation, suppose that the IQ score of 400 bird species have an average of 200, and the pigeon's score is 242, which has standard unit 1.5. this means the standard deviation of the 400 scores is ?
1) can't determined based of the given info
2) 42÷1.5
3) 42 * 1.5
4) 42