A researcher predicts that watching a film on institutionalization will change students’ attitudes about chronically mentally ill patients

A researcher predicts that watching a film on institutionalization will change students’ attitudes about chronically mentally ill patients. The researcher randomly selects a class of 36 students, shows them the film, and gives them a questionnaire about their attitudes. The mean score on the questionnaire for these 36 students is 70. The score for a similar class of students who did not see the film is 75. The standard deviation is 12. Using the five steps of hypothesis testing and the 5% significance level (i.e. alpha = .05), does showing the film change students’ attitudes towards the chronically mentally ill?

What does it mean to set alpha at .05? 
What is your null hypothesis? Alternate hypothesis? 
Is this a one-tailed or two-tailed hypothesis? 
What is the criterion z? 
Suppose the obtained z was -2.5. Do you reject or fail to reject the null hypothesis? 
State in words what you have found.

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