This is an assignment that discusses the PICO principles elements identification and research. The paper also discusses the potential impact of the procedures.

## The PICO principles elements identification and research

1. Study Design [35] 1.1 Briefly describe the research question that this paper aimed to address (no more than 250 words). [2]

1.2 i) Firstly, apply the PICO (population (P), intervention (I), comparison (C) and outcome(s) (O)) principle, to identify each of the P-I-C-O elements of the study. [5]

ii) What is the primary outcome of this research? Justify your answer. [2]

1.3 The authors describe the study as a “Single blind randomized clinical trial.” i) State the randomization procedure the authors used in this study. [2]

ii) Also, describe the “blindness” status in this study. [2]

iii) Then, discuss any potential impact of these two procedures on the validity of the study results. [4]

iv) Secondly, propose an alternative randomization approach which is different from what had been used in this article. [3]

1.4 From a research terminology view point, is this i) an experimental/observational, ii) prospective/retrospective and iii) cross-sectional/longitudinal study? Please justify your answer. [6]

1.5 Thirdly, briefly propose a different study design (other than a randomized clinical trial) to compare the effectiveness of two different doses of fluoride toothpaste in improving oral health. Comparing the study design that you have proposed to the one proposed by the authors, list two strengths and two weaknesses of the design you have suggested. [9]

### The PICO principles elements identification and research

2. This question focuses on the “Subjects” section of the paper: [9]

2.1) The authors used “DMFS>=5“ as an inclusion criterion to recruit “caries-active adolescents”. Identify “DMFS” variable’s type (qualitative/quantitative, categorical/binary/ordinal/nominal/continuous/discrete). [6]

2.2) Fourthly, provide 3 possible values that the variable DMFS can take. [3]

3. This question focuses on Table 1, which summarizes the baseline caries condition of the subjects in the two arms. [21]

3.2) The second row of Table 1 (extract shown below) shows the DiFS different at the baseline for the two arms. Assume DiFS is a normally distributed variable for this question. Use the table below to answer the following questions: [13]

3.2.1) Then, determine the DiFS range for the 5000ppm group that 70% of the participants (roughly 73 out of 104) fall into. [4]

3.2.2) For the 5000ppm group, if another random sample of 104 participants was selected from the same population, what is the chance that the average DiFS of this new sample will be over 16 surfaces? Show your calculation and interpret the results. [5]

3.2.3) Use your own words to explain the terminology: “Standard Error” and “Standard Deviation”. [4]

4. Using the results from Table 3, conduct a statistical test to answer the following question: Does the “Prevented Fraction in Progression” in Compliance B group outperform the Prevented Fraction in Compliance A Group? Write down the null and alternative hypotheses, state the statistical method used, conduct the analysis, report the estimates, and write a paragraph regarding your interpretation. Set the type one error to be 0.05. [8]

### The PICO principles elements identification and research

5. For this question, note that details of the sample size calculations are given under the “Statistical Methods” section of the article. [27]

5.1 Also, list 4 key elements, and their values, as used by the authors for the sample size calculation. [4]

5.2 Then, explain in your own words what “Type I errors (alpha)” and “Type II errors” are in statistics, using the sample size determination context given by the authors. [6]

5.3 What is the sample size by the sample size calculation? What is the total sample size adopted by the authors in this study? Additionally, are these two numbers the same or different (which is bigger)? Give a reason why this might be the case. [4]

5.4. Consider a situation when a study failed to recruit the sample size originally planned for (for example, if in the current study PI could only recruit 80 subjects). Explain the potential impact of using this smaller sample size on the data analysis. [4]

5.5 In general terms, briefly describe the effect on the sample size if the power was increased to 99%. [2]

5.6. Lastly, consider the situation that the authors want to plan a new follow-up study, and have recruited you as the trial statistician. You are to also conduct a new sample size calculation with alpha (2-sided) changed to 20%, from the original study design, and other elements remaining the same. Finally, show your calculation (pen/paper or a screen shot if using online sample size calculation tool). Give advice to PI how many subjects should he/she recruit? [7]