Conducting a z Test

Module 2: Assignment 2: Conducting a z-Test

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 people in general on this questionnaire is 75, with a standard deviation of 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?
Questions:

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 critical z?

Calculate the obtained z. Do you reject or fail to reject the null hypothesis?

State in words what you have found.

Answers:

What does it mean to set alpha at .05? It means that the set probability of the possibility of being incorrect is .05 if the null hypothesis is correct.

What is your null hypothesis? Alternate hypothesis? Null hypothesis: The mean score on the questionnaire of the group watching the film is statistically equal to the mean score for the group that did not watch the movie. Alternate hypothesis: Watching a film on institutionalization will change students’ attitudes about chronically mentally ill patients. The mean score for the group watching the film will be statistically different from the mean score for the group that did not watch the film.

Is this a one-tailed or two-tailed hypothesis? Two-tailed

What is the critical z? The z for alpha = .05 are -1.96 and +1.96., thus I would reject the null hypothesis if z < -1.96 or z > +1.96

Calculate the obtained z. Do you reject or fail to reject the null hypothesis? I reject, as z=-2.5

State in words what you have found. There is a statistical difference between the mean scores of the two groups, which implies that the film did change students’ attitudes towards the chronically mentally ill.