Statistical Hypothesis Testing
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?
Alpha means making a Type I error same as significance level. When the alpha is at .05 it means that the researcher doesn’t want to take a big risk therefore sets the alpha to .05. By doing this it will make it hard for hypothesis testing process to reject the null hypothesis unless it is extreme. α=0.05 means: P (type I error) = 0.05, rejecting Ho being Ho true is 0.05
What is your null hypothesis? And Alternate hypothesis?
The null hypothesis would be that watching films on institutionalization will change students’ attitudes about chronically mentally ill patients. The Alternative Hypothesis would be that watching films on institutionalization will not change students’ attitudes about chronically mentally ill patients.
Ho: μ=75 (Null)
Ha: μ≠ 75 (Alternate)
Is this a one-tailed or two-tailed hypothesis?
The hypothesis is two-tailed since we are using a significance level of 0.05. Therefore, no matter the direction you are hypothesizing the researcher is testing for the possibility on both sides since the alternative is: Ha: μ≠ 75 it is two-tailed What is the criterion z?
(70-75)/ (sd/√n) = -5/ (12/√36) = -2.5 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
What does it mean to set alpha at .05?
Alpha means making a Type I error same as significance level. When the alpha is at .05 it means that the researcher doesn’t want to take a big risk therefore sets the alpha to .05. By doing this it will make it hard for hypothesis testing process to reject the null hypothesis unless it is extreme. α=0.05 means: P (type I error) = 0.05, rejecting Ho being Ho true is 0.05
What is your null hypothesis? And Alternate hypothesis?
The null hypothesis would be that watching films on institutionalization will change students’ attitudes about chronically mentally ill patients. The Alternative Hypothesis would be that watching films on institutionalization will not change students’ attitudes about chronically mentally ill patients.
Ho: μ=75 (Null)
Ha: μ≠ 75 (Alternate)
Is this a one-tailed or two-tailed hypothesis?
The hypothesis is two-tailed since we are using a significance level of 0.05. Therefore, no matter the direction you are hypothesizing the researcher is testing for the possibility on both sides since the alternative is: Ha: μ≠ 75 it is two-tailed What is the criterion z?
(70-75)/ (sd/√n) = -5/ (12/√36) = -2.5 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