Case: Some experts in public health have proposed to cut tobacco-related deaths by reducing nicotine levels in cigarettes. However, critics of this proposal have argued that smokers would simply compensate by increasing the number of cigarettes smoked, thereby maintaining or even increasing the overall nicotine levels consumed in a day. The Ministry of Health has commissioned a group of medical researchers to conduct a randomized controlled trial to examine this issue.

The researchers recruited 20 male smokers who were 18 years or older, smoked five or more traditional cigarettes (i.e., tobacco cigarettes and not e-cigarettes) per day, and had no current interest in quitting smoking. They randomly assigned the participants to receive either one of two types of traditional cigarettes: Cigarettes with a typical nicotine level (15.8 mg of nicotine per gram) or cigarettes with a reduced nicotine level (2.4 mg of nicotine per gram). Participants were not told which type of cigarettes they were smoking. The researchers then tracked the number of the assigned cigarettes smoked over a six-week period.

The average number of assigned cigarettes smoked in a day for each of the 20 participants is presented in the table below.

Average Number of Assigned Cigarettes Smoked Daily

Cigarettes with A Typical Nicotine Level (15.8 mg)
21.74
18.78
23.45
21.43
26.97
24.68
20.30
17.48
21.93
17.05

Cigarettes with A Reduced Nicotine Level (2.4 mg)
11.33
15.72
22.82
18.15
12.10
16.74
19.35
12.40
18.67
23.53

Note 1. The average number of cigarettes each group consumed before the study was not significantly different. In other words, the nicotine habits were not significantly different between the two groups.
Note 2. For the purposes of this exercise, we are using a small sample size. However, in the real world, a much larger sample with more observations would be recommended for reliable results.

Question 1: Identify the predictor variable. State the number of levels/conditions and identify what the levels/conditions are. Identify the outcome variable.

Question 2: Identify the scale of measurement of the predictor variable and explain why.

Question 3: Identify the scale of measurement of the outcome variable and explain why.

Question 4: Identify if this is an experimental or observational study. Explain why in the context of this study to support your answer.

Question 5: Identify if this is a between-subjects or within-subjects design. Explain why in the context of this study to support your answer.

Question 6: Based on the study design, identify the most appropriate parametric statistical test to conduct. Discuss why this is the most appropriate parametric test by providing two reasons in the context of this study.

Question 7: State the null hypothesis (H0) and the non-directional alternative hypothesis (H1).

Question 8: Assuming all the assumptions of the statistical test you identified in (f) are met and there are no concerns about small sample size, analyse the data using jamovi. Show the jamovi spreadsheet by taking a screenshot of the spreadsheet (i.e., what you see when you click the DATA tab) and pasting it in your answer. The jamovi spreadsheet should be correctly formatted. Further, paste all the output necessary for interpretation of the results in your answer.

Question 9: Interpret the results of your data analysis. Explain your answer with reference to the p value, the alpha level, and the descriptives. Use an alpha level of .05.

Question 10: Report the results in A_P_A format(Stats format) and state what recommendation the researchers should make to the Ministry of Health.

Question 11: Discuss two limitations to this study and how you might change this study to address the limitations.