PSYCH 625 Time to Practice – Week Three
Part A
Some questions in Part A require that you access data from Statistics for People Who (Think They) Hate Statistics. This data is available on the student website under the Student Test Resources link.
1. For the following research questions, create one null hypothesis, one directional research hypothesis, and one nondirectional research hypothesis.
a. What are the effects of attention on outofseat classroom behavior?
Research Hypothesis: There will be a relationship between the effects of attention on outofseat classroom behavior versus inseatclassroom behavior.
b. What is the relationship between the quality of a marriage and the quality of the spouses’ relationships with their siblings?
Null Hypothesis: There will be no relationship in the relationship between the quality of a marriage and the quality of the spouses’ relationship with their siblings.
c. What is the best way to treat an eating disorder?
One Directional Research Hypothesis:
2. Provide one research hypothesis and an equation for each of the following topics:
a. The amount of money spent on food among undergraduate students and undergraduate studentathletes
b. The average amount of time taken by white and brown rats to get out of a maze
c. The effects of Drug A and Drug B on a disease
d. The time to complete a task in Method 1 and Method 2
3. Why does the null hypothesis presume no relationship between variables?
4. Create a research hypothesis tested using a onetailed test and a research hypothesis tested using a twotailed test.
5. What does the critical value represent?
6. Given the following information, would your decision be to reject or fail to reject the null hypothesis? Setting the level of significance at .05 for decision making, provide an explanation for your conclusion.
a. The null hypothesis that there is no relationship between the type of music a person listens to and his crime rate (p < .05).
In Hypothesis Testing, we typically deem a research hypothesis to be significant, if the odds of two means actually being equal are no greater than 1 in 20 or .05 (5%) or less.
b. The null hypothesis that there is no relationship between the amount of coffee consumption and GPA (p = .62).
c. The null hypothesis that there is a negative relationship between the number of hours worked and level of job satisfaction (p = .51).
7. Why is it harder to find a significant outcome (all other things being equal) when the research hypothesis is being tested at the .01 rather than the .05 level of significance?
At the .01 level, there is less room for error because the test is more rigorous.
8. Why should we think in terms of “failing to reject” the null rather than just accepting it?
9. When is it appropriate to use the onesample z test?
10. What similarity does a z test have to a simple z or standard score?
11. For the following situations, write out a research hypothesis:
a. Bob wants to know if the weight loss for his group on the chocolateonly diet is representative of weight loss in a large population of middleaged men.
b. The health department is charged with finding out if the rate of flu per thousand citizens for this past flu season is comparable to the average rate of the past 50 seasons.
c. Blair is almost sure that his monthly costs for the past year are not representative of his average monthly costs over the past 20 years.
12. There were about 15 flu cases per week, this flu season, in the Oshkosh school system. The weekly average for the entire state is 16 and the standard deviation, is 2.35. Are the kids in Oshkosh as sick as the kids throughout the state?
From Salkind (2011). Copyright © 2012 SAGE. All Rights Reserved. Adapted with permission.
Part B
Complete the following questions. Be specific and provide examples when relevant.
Cite any sources consistent with APA guidelines.
Question 
Answer 

The average raw math achievement score for third graders at a Smith elementary school is 137; third graders statewide score an average of 124 with a standard deviation of 7. Are the Smith third graders better at math than third graders throughout the state? Perform the correct statistical test, applying the eight steps of the hypothesis testing process as demonstrated on pp. 185–187 of Statistics for People Who (Think they) Hate Statistics. 


What is a research question that you would like to answer? Write the null and research hypotheses. Would you use a one or twotailed test? Why? 


What do we mean when we say that a statistical result is significant? What is the difference between a statistically significant and a meaningful result? Why is statistical significance important? 
The meaning of a statistical result is significant is basically saying that the probability that an effect is not due to chance by itself, so basically it is a value judgment. In essence any result in statistics is not considered significant because it is important rather it has basically been predicted as unlikely to have occurred by chance alone. The difference between statistically significant and meaningful result is that statistically significant means that data is below a certain alpha level, which basically means that it is considered significant in terms of numbers. Now, meaningful result is something that is meaningful in real life. So for example” Say that 10% of heart surgeries fail, and the desired alpha level is 5%. This data would not be statistically significant because it is above the alpha level so statisticians would say it has not meaning, but that is does have meaningful results because in real life 10% of failed heart surgeries bears real life meaning to those that are considering having heart surgery. Statistical significance is important because it is a mathematical tool that is used to determine whether the outcome of an experiment is the result of a relationship between specific factors or merely the result of chance. 

Describe a Type I error for the previous study that compares third graders’ math achievement. Describe a Type II error for that study. 
A Type II error of study could typically be presented in this example: 
