Module 06 Knowledge Check
5 questions. Pass mark 4 out of 5. Answer every question before checking the answer key below, then retry after reading the feedback.
1. A large gap between the mean and the median tells you…
- A. one of them was computed wrongly
- B. the data is skewed, usually by extreme values
- C. the sample is too small
- D. the column has missing values
2. Including n() in every grouped summary matters most because…
- A. summarise() requires it
- B. a group with very few rows will often top the ranking
- C. it speeds up the grouping
- D. it prevents missing values
3. The mean of three group means equals the overall mean only when…
- A. the groups have equal size
- B. the data is normally distributed
- C. there are no missing values
- D. the groups are sorted
4. 'North accounts for a third of the waiting list' is a…
- A. row percentage describing North's performance
- B. column percentage describing where the queue sits
- C. rate comparable between wards
- D. count
5. Keeping a Months reported column in a report table matters because…
- A. it fills space
- B. it lets a reader judge whether the rate is comparable
- C. kable requires it
- D. it is needed for sorting
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Answer Key and Explanations
Check these only after attempting every question.
1. B — the data is skewed, usually by extreme values
The gap is itself a finding. The mean uses every value's size; the median only its rank.
2. B — a group with very few rows will often top the ranking
Without the count, a mean of one observation looks exactly like a mean of twelve and the ranking reads as settled.
3. A — the groups have equal size
Averaging averages weights each group equally regardless of how much data it contains.
4. B — column percentage describing where the queue sits
It divides by the total waiting, so it depends on how large North is. North's own waiting rate may be the lowest of all.
5. B — it lets a reader judge whether the rate is comparable
A rate without its denominator invites a conclusion the data cannot support, and omitting the column is an invisible decision.
Practical Check
Apply this module to your own work: complete the module activity for *Descriptive Summaries and Basic Tables*, then write one sentence naming what your result shows and one naming what it does not.
Strong Answer Pattern
A strong answer names the task, the evidence used, the check performed, and the remaining limitation. It avoids "proved", "guaranteed", or "always" unless the evidence genuinely supports it.