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 and why? 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.
Hi,
I am working on them now
Steve
Thanks so much!
Answers:
What does it mean to set alpha at .05?
α=0.05 means: P(type I error) = 0.05
In other words: The probability of rejecting Ho being Ho true is 0.05
What is your null hypothesis? Alternate hypothesis?
Ho: μ=75
Ha: μ≠ 75
Is this a one-tailed or two-tailed hypothesis and why?
Two tailed, since the alternative is: Ha: μ≠ 75
What is the criterion z?
Can you check this question ?
Suppose the obtained z was -2.5.
Do you reject or fail to reject the null hypothesis?
Critical values are -z(0.025)=-1.96 and z(0.025)=1.96
Rejection region: {z/z<-1.96 or z>1.96}
Since z = -2.5 <-1.96 we reject Ho
Thanks
Hi Steve,That's exactly what the questions says: What is the criterion z? Also, can you show me how you made the calculations and explain what the findings mean? The more detail the better. Statistics is like a foreign language to me.
Ok,
I will add some work now, wait a minute
Thanks so much! I really appreciate it!
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?
Introduction:
We have the group sampled (they saw the film)
Sample size is n = 36
Mean is 75
Standard deviation is 12
And we know the mean for students that they didn´t see the film (this mean is 70)
The question asks if the mean changes
So we have to test (or confirm) if the mean is not 70 for the group sampled
Then at this point we can ask this question:
Ho: μ=75 (Null)
Ha: μ≠ 75 (Alternate)
We can make 2 error (Type I and Type II)
Type I error is: Rejecting Ho being Ho true
z-statistic = (70-75)/(sd/√n) = -5/(12/√36) = -2.5
Suppose the obtained z was -2.5. (it was computed above)
Critical values are -z(0.025)=-1.96 and z(0.025)=1.96 (using excel)
Thank you
If you have more questions and if you want my help just write "For Steve" into a new post