Before running our statistical test, we should test for normality. Which of the following is the correct way to do this on this dataset?

Question

BlackTom AI · Accepted Answer

Shapiro-Wilk requires a numeric vector input, so apply it separately to each group's attendance vector: shapiro.test(otherland$attendance) and shapiro.test(bunnyland$attendance).

1) Relevant knowledge points and concepts
- The Shapiro-Wilk test in R is invoked as shapiro.test(x) where x is a numeric vector of observations.
- When comparing two groups (e.g., two locations) and checking the normality assumption for a two-sample test, assess normality separately for each group's distribution.
- The test returns a W statistic and a p-value; p > 0.05 typically indicates failure to reject normality (approx. normal).

2) Step-by-step reasoning process
- Identify the grouping variable (location: otherland vs bunnyland) and the numeric response (attendance).
- Extract attendance values for each group (e.g., otherland$attendance and bunnyland$attendance).
- Run shapiro.test on each extracted vector to assess normality per group.

3) Intermediate steps / example code
- otherland <- subset(d, location == "otherland")
- bunnyland <- subset(d, location == "bunnyland")
- shapiro.test(otherland$attendance)
- shapiro.test(bunnyland$attendance)
No numeric computation beyond these function calls is required here.

4) Why the correct answer is correct
- Because shapiro.test expects a numeric vector, the correct procedure is to pass each group's attendance vector separately. This directly tests the normality assumption for each sample before choosing parametric or nonparametric comparisons.

5) Why the other options are incorrect
- shapiro.test(d$attendance): tests the pooled distribution, not each group separately.
- shapiro.test(attendance ~ otherland - bunnyland, data=d) and shapiro.test(location ~ attendance, data=d): shapiro.test does not accept a formula interface; these are invalid usages.
- None of the above: incorrect because a valid option is provided.

6) Conclusion
The correct approach is shapiro.test(otherland$attendance) and shapiro.test(bunnyland$attendance), which matches the provided answer.

Before running our statistical test, we should test for normality. Which of the following is the correct way to do this on this dataset?单项选择题

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