Answer to Question 1
The original researchers claimed that listening to music led to improved scores in spatial tasks. Subsequently Steele and his colleagues and Thompson and colleagues varied types of music to which participants listened. When these researchers replicated the original studies, they found that arousal levels and mood accounted for the effect. So psychologists now believe that listening to Mozart does not have a specific effect on cognitive processes.
Answer to Question 2
Your sampling frame includes all the potential respondents you could contact. If you don't have a complete list of your population, it is impossible to define a method that would lead to a probabilistic sample. Such a sample requires knowledge of the population. Without a probabilistic sample, you don't know to whom you can generalize.
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