Difficult and failed tracheal intubations are among the principal causes of anesthetic-related mortality and morbidity. Because a good laryngeal view facilitates successful tracheal intubation, new technologies have been introduced to improve visualization. The Pentax AWS is a novel video laryngoscope, available in Japan since 2006, which is designed to facilitate intubation by providing a video image of the glottis. Abdallah et al. conducted a study to examine whether intubation with the Pentax AWS would be easier and faster than with a standard Macintosh laryngoscope with a #4 blade. The sample included 99 adult patients having a body mass index between 30 and 50 kg/m² who required orotracheal intubation for elective surgery.

The variables collected included: GRP (1=Pentax AWS, 0=Macintosh #4 blade), AGE (years), GENDER (1=male, 0=female), BMI (body mass index in kg/m²), ASA (American Society of Anesthesiologists physical status where 1=I, 2=II, 3=III, 4=IV), MALLAMPATI (score predicting ease of intubation where 1=Full visibility of tonsils, uvula and soft palate; 2=Visibility of hard and soft palate, upper portion of tonsils and uvula; 3=Soft and hard palate and base of the uvula are visible; 4=Only hard palate visible), and VIEW (Cormack-Lehane grade of glottic view where 0="not good" Cormack-Lehane grade 1 or 2; 1="good" Cormack-Lehane grade 3 or 4), INTUBTIME (intubation time in seconds), and EASE (actual ease of tracheal intubation where 0=extremely easy and 100=extremely difficult). Note that patients missing data were excluded from the analysis.

For questions 1-5, examine the computer output of the five different models provided for you at the end of this quiz labeled SAS Output #1-SAS Output #5. Match the output with the most appropriate analysis. You may select each letter (method) more than once, once, or not at all.

(1 point each)

1.SAS Output #1 a.Multiple linear regression

2.SAS Output #2 b.ANCOVA

3.SAS Output #3 c.One-way ANOVA

4.SAS Output #4 d.Two-way ANOVA with an interaction

5.SAS Output #5 e.Two-way ANOVA without an interaction

For questions 6-22, refer to SAS Output #1 and the following: Using a 0.05 significance level, you now need to test the claim that the means for actual ease of tracheal intubation scores differed between patients in the 4 Mallampati score categories by answering the questions below.

6.What are the omnibus null and alternative hypotheses? (1 point)

a.H₀: ₁ = ₂ = ₃ = ₄ = 0, H₁: at least one _i 0

b.H₀: ₁ = ₂ = ₃ = ₄, H₁: _{1 2 3 4}

c.H₀: ₁ = ₂ = ₃ = ₄, H₁: _{1 2 3 4}

d.H₀: ₁ = ₂ = ₃ = ₄, H₁: at least one _i differs from another _j

e.H₀: ₁ = ₂ = ₃ = ₄, H₁: at least one _i differs from another _j

7.What are the independent and dependent variables? (1 point)

a.Dependent = Mallampati score, independent = intubation time

b.Dependent = intubation time, independent = Mallampati score

c.Dependent = Mallampati score, independent = ease of tracheal intubation score

d.Dependent = ease of tracheal intubation score, independent = Mallampati score

e.Cannot be determined from the given information.

8.How many patients were used in this model? (0.5 point)

a.95

b.96

c.97

d.98

e.99

For questions 9-14 refer to the following: In the first table of SAS Output #1, several important values have been replaced with the letters A-G. You need to find these missing values.

9.Model Degrees of Freedom (labeled A) (0.5 point)

a.1

b.2

c.3

d.4

e.5

10.Error Degrees of Freedom (labeled B) (0.5 point)

a.92

b.93

c.94

d.95

e.96

11.Sum of Square Error (labeled C) (0.5 point)

a.55.88

b.494.74

c.950.15

d.89314.02

e.92569.10

12.Mean Square Model (labeled D) (0.5 point)

a.325.51

b.406.89

c.542.51

d.813.77

e.1627.54

13.Mean Square Error (labeled E) (0.5 point)

a.930.35

b.940.15

c.950.15

d.960.37

e.970.80

14.t test statistic (labeled F) (0.5 point)

a.-11.5

b.-0.68

c.0.46

d.0.50

e.0.57

15.What is the value of the test statistic for the omnibus null hypothesis H₀? (1 point)

a.-0.09

b.0.57

c.0.64

d.0.76

e.3.33

16.What is the p-value corresponding to the test statistic in question (15)? (0.5 point)

a.0.05

b.0.36

c.0.50

d.0.64

e.0.93

17.Using a 0.05 significance level, what decision and conclusion should you make regarding the omnibus null hypothesis? (1 point)

a.Because p-value < 0.05, we reject H₀ and conclude that patients in at least one Mallampati score category have a significantly different mean ease of intubation score than the others.

b.Because p-value < 0.05, we fail to reject H₀ and conclude that the mean ease of intubation score does not differ significantly between patients in the four Mallampati score categories.

c.Because p-value > 0.05, we fail to reject H₀ and conclude that the mean ease of intubation score does not differ significantly between patients in the four Mallampati score categories.

d.Because p-value > 0.05, we fail to reject H₀ and conclude that patients in all four Mallampati score categories have a significantly different mean ease of intubation score from one another.

e.Because p-value > 0.05, we reject H₀ and conclude that the mean ease of intubation score does differ significantly between patients in the four Mallampati score categories.

18.Assuming you rejected the omnibus null hypothesis in question 17 (this may or may not be true), what test should you conduct next? (1 point)

a.Tukey test

b.Bonferroni test

c.Multiple comparisons test

d.Any of the above are appropriate

e.None of the above are appropriate

19.What is the estimated mean ease of intubation score for each of the four Mallampati score categories? (1 point)

a.₁ = -1.39, ₂ = -7.87, ₃ = -11.5, ₄ = 0

b.₁ = -1.39, ₂ = -7.87, ₃ = -11.5, ₄ = 0

c.₁ = -1.39, ₂ = -7.87, ₃ = -11.5, ₄ = 51.25

d.₁ = -1.39, ₂ = -7.87, ₃ = -11.5, ₄ = 51.25

e.₁ = 49.86, ₂ = 43.38, ₃ = 39.75, ₄ = 51.25

f.₁ = 49.86, ₂ = 43.38, ₃ = 39.75, ₄ = 51.25

20.Do any of the four Mallampati score categories differ significantly in their mean ease of intubation score? If so, which one(s) differ? (1 point)

a.Yes, _{2 4}

b.Yes, _{3 4}

c.Both a and b

d.No, the mean ease of intubation score does not differ significantly between the four Mallampati score categories.

e.Cannot be determined from the given information.

21.What types of variation, if any, are being analyzed in this problem? (1 point)

a.We are comparing the mean ease of intubation score for four groups, which has nothing to do with variation.

b.Variation in ease of intubation score between Mallampati score categories

c.Variation in ease of intubation score within Mallampati score categories

d.Both b and c

e.None of the above

22.Is there a reference cell in this problem? If so, what is it? (1 point)

a.Yes, the reference cell is Mallampati score category 1.

b.Yes, the reference cell is Mallampati score category 2.

c.Yes, the reference cell is Mallampati score category 3.

d.Yes, the reference cell is Mallampati score category 4.

e.Yes, there is a reference cell, but the group cannot be determined with the given output.

f.No, there is no reference cell.

23.Suppose the researchers are interested in comparing the ease of intubation score between the Pentax AWS and Macintosh #4 blade groups, adjusted for the patient's age, gender, and Cormack-Lehane grade of glottic view. Using the most appropriate model, select which of the following statements is true. (1 point)

a.Mean ease of intubation score differs significantly based on laryngoscope group, age, gender, and Cormack-Lehane grade of glottic view.

b.Mean ease of intubation score does not differ significantly based on laryngoscope group, age, gender, or Cormack-Lehane grade of glottic view.

c.Mean ease of intubation score differs significantly based on age and gender but not laryngoscope groups or Cormack-Lehane grade of glottic view.

d.Mean ease of intubation score differs significantly between laryngoscope groups, after adjusting for age, gender, and Cormack-Lehane grade of glottic view.

e.Mean ease of intubation score does not differ significantly between laryngoscope groups, after adjusting for age, gender, and Cormack-Lehane grade of glottic view.

24.The interaction plot below was generated from the model in SAS Output #2. What can you say about the following figure? Before selecting an answer, take a close look at the relevant p-value(s) in SAS Output #2, too. (1 point)

a.There is a statistically significant same direction interaction between laryngoscope group and gender.

b.There is a statistically significant reverse interaction between laryngoscope group and gender.

c.While the figure shows a same direction interaction between laryngoscope group and gender, the interaction is not statistically significant.

d.While the figure shows a reverse interaction between laryngoscope group and gender, the interaction is not statistically significant.

e.The mean ease of intubation score is significantly higher for females than males.