All questions
Question 1
A museum records the amounts (in dollars) donated by 60 visitors during a weekend fundraiser. The five-number summary is: min =1, Q1=5, median =12, Q3=25, max =120. A modified boxplot (1.5·IQR rule) is drawn. Which feature is consistent with the summary statistics?
- The range is 25−5=20 dollars.
- The IQR is 120−1=119 dollars.
- The box extends from Q1=5 to Q3=25, with a median line at 12. (correct answer)
- The right whisker must extend to 120 dollars because it is the maximum donation.
- Because the maximum is large, the median must be greater than Q3.
Explanation: This question tests understanding of modified boxplot construction with the 1.5·IQR rule. The box always extends from Q₁ to Q₃ with the median line inside. Given Q₁ = 5, Q₃ = 25, and median = 12, the box extends from 5 to 25 dollars with the median at 12 dollars, making choice C correct. Choice A incorrectly identifies the IQR as the range; IQR = Q₃ - Q₁ = 25 - 5 = 20 dollars. Choice B incorrectly calculates IQR using max - min. Choice D is incorrect because with IQR = 20, the upper fence = 25 + 1.5(20) = 55, so 120 would be plotted as an outlier point, not connected by the whisker. Choice E makes a logical error; the median cannot be greater than Q₃ by definition, as Q₃ represents the 75th percentile while the median is the 50th percentile.
Question 2
All data values are multiplied by 3. What happens to the boxplot's box length?
- It remains unchanged
- It is multiplied by 3 (correct answer)
- It increases by 3
- Cannot be determined
Explanation: The box length is the interquartile range (IQR), the difference between the third and first quartiles. Multiplying every data value by 3 also multiplies both quartiles by 3, so their difference is multiplied by 3. The tempting mistake is thinking the box length stays unchanged, but scaling the data scales all measures of spread, including the IQR.
Question 3
A boxplot has Q1=40, median=50, Q3=80. Which description is most plausible?
- Left-skewed; mean < 50
- Symmetric; mean near 50
- Right-skewed; mean > 50 (correct answer)
- Bimodal; mean near 50
Explanation: The box's right half (median 50 to Q3 80) is much longer than its left half (Q1 40 to median 50), so the distribution is right-skewed. In a right-skewed distribution, the mean is pulled toward the longer tail, so it is greater than the median. Symmetric near 50 is tempting but wrong because the two box halves are clearly unequal.
Question 4
Five-number summary: 4,8,12,18,36. By the 1.5(IQR) rule,
- Only 18 is an outlier
- 4 and 36 are outliers
- There are no outliers
- Only 36 is an outlier (correct answer)
Explanation: The IQR is 18 - 8 = 10. Times 1.5 gives 15, so the fences are 8 - 15 = -7 and 18 + 15 = 33. The only value beyond a fence is 36, above 33, so only 36 is an outlier. The tempting mistake is thinking 4 is an outlier because it's far from the median, but it is well above the lower fence -7.
Question 5
Which statement about a standard boxplot is true?
- It shows the mean as a line
- It displays every data value
- It requires normal data
- It can hide multiple peaks (correct answer)
Explanation: A standard boxplot summarizes data with the median, quartiles, and whiskers, so it does not display the actual distribution shape and can hide multiple peaks. The mean is shown as a line only in some modified plots, not a standard boxplot; the center line is the median.
Question 6
Ignoring outliers, a zero-length left whisker means
- Minimum equals Q1 (correct answer)
- Q1 equals the median
- Median equals Q3
- Maximum equals Q3
Explanation: In a boxplot, the left whisker runs from the minimum to Q1. If its length is zero, those two endpoints are the same point, so the minimum equals Q1. The tempting mistake is to think it means Q1 equals the median, but that would make the left edge of the box touch the median line, not shorten the whisker.
Question 7
A school nurse records the number of absences for each of 80 students in a semester. The five-number summary (absences) is: min =0, Q1=1, median =3, Q3=6, max =15. A boxplot is drawn using these values (no outliers marked). Which feature is consistent with the summary statistics?
- The median is at 6 absences.
- The left whisker extends from 1 down to 0 absences. (correct answer)
- The interquartile range is 15−0=15 absences.
- The box extends from 0 to 15 absences.
- The maximum value (15) must be shown as an outlier point, not as a whisker endpoint.
Explanation: This question tests understanding of whisker placement in boxplots. The left whisker should extend from Q1 down to the minimum value, which means from 1 down to 0 absences, making option B correct. Option A incorrectly places the median at Q3's value (6) instead of 3. Option C calculates a range (max - min = 15 - 0 = 15) rather than the IQR (Q3 - Q1 = 6 - 1 = 5). Option D incorrectly extends the box from min to max (0 to 15) instead of Q1 to Q3 (1 to 6). Option E misapplies outlier rules when the problem explicitly states no outliers are marked. Key concept: whiskers connect the box edges (Q1 and Q3) to the minimum and maximum values, not to each other.
Question 8
An environmental scientist records daily high temperatures (in ∘F) for 31 days in July in one city. The five-number summary is: min =71, Q1=78, median =83, Q3=88, max =97. A boxplot is drawn from these values. Which feature is consistent with the summary statistics?
- The right whisker extends from 88 to 97 ∘F. (correct answer)
- The median is at 88 ∘F.
- The IQR is 97−71=26 ∘F.
- The box extends from 71 to 97 ∘F.
- The left whisker ends at 78 ∘F because Q1 is the minimum.
Explanation: This question assesses understanding of whisker placement in temperature data. The right whisker extends from Q3 to the maximum value, which means from 88 to 97°F, making option A correct. Option B incorrectly places the median at Q3's position (88) when it should be at 83°F. Option C calculates max - min (97 - 71 = 26) and calls it the IQR, but the IQR should be Q3 - Q1 (88 - 78 = 10). Option D incorrectly extends the box from min to max (71 to 97) instead of Q1 to Q3 (78 to 88). Option E misunderstands the five-number summary; Q1 (78) is not the minimum value (71). Remember: whiskers show the data range beyond the quartiles, extending from the box edges to the extreme values.
Question 9
A streaming service samples 100 users and records the number of hours each user watched in the past week. The five-number summary (hours) is: min =0.5, Q1=3, median =6.5, Q3=11, max =26. A boxplot is made from these statistics (no outliers marked). Which feature is consistent with the summary statistics?
- The median line is drawn at 11 hours.
- The interquartile range is 26−0.5=25.5 hours.
- The box extends from 3 to 11 hours. (correct answer)
- The left whisker ends at 3 hours.
- The maximum (26) must be shown as an outlier point, so the right whisker ends at 11 hours.
Explanation: This question tests identification of the box portion in a boxplot with streaming data. The box extends from Q1 to Q3, which is from 3 to 11 hours, making option C correct. Option A incorrectly places the median at Q3's value (11) instead of 6.5 hours. Option B calculates max - min (26 - 0.5 = 25.5) rather than the IQR, which is Q3 - Q1 (11 - 3 = 8). Option D states a fact about the whisker endpoint but doesn't identify the distinguishing feature of the box. Option E introduces outlier rules that don't apply since the problem explicitly states no outliers are marked. Key concept: the box in a boxplot represents the interquartile range, containing the middle 50% of observations between Q1 and Q3.
Question 10
A farmer measures the weights (in pounds) of 48 pumpkins harvested from a field. The five-number summary is: minimum 6, Q1=10, median 13, Q3=18, maximum 33. A boxplot is drawn from these statistics (no outliers shown). Which feature is consistent with the summary statistics?
- The box extends from 6 to 33 pounds.
- The IQR is 33−6=27 pounds.
- The median is located at 13 pounds, between Q1 and Q3. (correct answer)
- The right whisker ends at 18 pounds.
- The range is 18−10=8 pounds.
Explanation: This question tests recognition of correct boxplot features from summary statistics. Given the five-number summary (min=6, Q1=10, median=13, Q3=18, max=33), we need to identify the correct statement. The box extends from Q1 to Q3 (10 to 18 pounds), not 6 to 33. The IQR is Q3-Q1 = 18-10 = 8 pounds, not 27. The median at 13 pounds is correctly positioned between Q1 (10) and Q3 (18), making choice C correct. The right whisker extends from Q3 to the maximum, ending at 33 pounds, not 18. The range is max-min = 33-6 = 27 pounds, not 8. When interpreting boxplots, the median line must always fall within the box, as it represents a value between the 25th and 75th percentiles of the distribution.
Question 11
A teacher records the scores (out of 100) on a quiz for 80 students. The five-number summary is: minimum 40, Q1=62, median 70, Q3=84, maximum 98. A boxplot is made using these values. Which feature is consistent with the summary statistics?
- The range is 84−62=22 points.
- The box extends from 62 to 84 points. (correct answer)
- The median line is drawn at 84 points.
- The left whisker ends at 62 points.
- Any score above 98 must be shown as an outlier on the boxplot.
Explanation: This question tests recognition of boxplot components from summary statistics. Given the five-number summary (min=40, Q1=62, median=70, Q3=84, max=98), we need to identify which statement correctly describes a boxplot feature. The box in a boxplot always extends from Q1 to Q3, which here is from 62 to 84 points, making choice B correct. The range is maximum minus minimum (98-40 = 58 points), not 22. The median line should be at 70 points, not 84. The left whisker extends from the minimum (40) to Q1 (62), not ending at 62. Without specific outlier rules given, we cannot determine if 98 would be an outlier. Remember that the box represents the interquartile range and contains the middle 50% of the data.
Question 12
A librarian tracked the number of books checked out by each visitor on a particular day (population: all 60 visitors that day). The five-number summary is: min =0, Q1=1, median =2, Q3=4, max =12. A boxplot is drawn. Which feature is consistent with the summary statistics?
- The median is at 4 because Q3=4.
- The box extends from 1 to 4 with a median line at 2. (correct answer)
- The range is 4−1=3 books.
- The whiskers extend from 1 to 4, and the box extends from 0 to 12.
- The maximum value 12 must be plotted as an outlier point beyond the whisker.
Explanation: This question assesses understanding of boxplot construction from summary statistics. The box extends from Q₁ (1) to Q₃ (4), with the median line at 2 positioned inside this box. The whiskers extend from the box edges to the minimum (0) and maximum (12) values. Choice B correctly identifies that the box extends from 1 to 4 with a median line at 2. Common misconceptions in the distractors include: confusing Q₃ with the median, calculating range instead of identifying boxplot features (range is 12-0=12, not 3), reversing box and whisker positions, and assuming extreme values must be outliers. Remember that in a standard boxplot from a five-number summary, all five values are incorporated into the plot structure.
Question 13
A teacher summarizes scores (out of 50) on a quiz for 90 students. The five-number summary is: min =11, Q1=29, median =34, Q3=41, max =49. A boxplot is drawn from these values. Which feature is consistent with the summary statistics?
- The median is drawn at 41.
- The box extends from 29 to 41, and the median line is at 34. (correct answer)
- The interquartile range is 49−11=38.
- The left whisker ends at 29 because Q1 is the minimum.
- The right whisker ends at 34 because the median is the largest value shown by a whisker.
Explanation: This question tests comprehensive boxplot interpretation with quiz scores. The box extends from Q1 to Q3 (29 to 41), and the median line is drawn at 34, making option B correct. Option A incorrectly places the median at Q3's position (41) instead of 34. Option C calculates the range (max - min = 49 - 11 = 38) rather than the IQR, which is Q3 - Q1 (41 - 29 = 12). Option D incorrectly claims Q1 equals the minimum; Q1 is 29 but the minimum is 11. Option E makes no sense as whiskers extend to extreme values, not to the median. Remember: reading a boxplot requires identifying five key values - the minimum, Q1, median, Q3, and maximum - each serving a specific role in the display.
Question 14
A coffee shop measures the wait time (in minutes) for 70 customers during the morning rush. The five-number summary is: min =2, Q1=4, median =6, Q3=9, max =20. A boxplot is constructed using these values (no outliers marked). Which feature is consistent with the summary statistics?
- The median is drawn at 9 minutes.
- The range is 9−4=5 minutes.
- The box extends from 4 to 9 minutes. (correct answer)
- The left whisker ends at 4 minutes.
- The maximum (20) must be plotted as an outlier point rather than as the whisker endpoint.
Explanation: This question tests recognition of the box component in a boxplot. The box extends from Q1 to Q3, which is from 4 to 9 minutes, making option C correct. Option A incorrectly places the median at Q3's value (9) instead of 6. Option B calculates Q3 - Q1 (9 - 4 = 5) but mislabels it as the range rather than the IQR; the range would be max - min = 20 - 2 = 18. Option D correctly identifies where the left whisker ends but this isn't the distinguishing feature asked for. Option E introduces outlier considerations that aren't applicable since the problem states no outliers are marked. Key insight: the box in a boxplot always spans from the first quartile to the third quartile, representing where the middle half of the data falls.
Question 15
A cross-country coach measured the distances (in miles) run by each athlete during a Saturday practice (population: all 32 athletes on the team). The five-number summary is: min =2.0, Q1=3.5, median =4.2, Q3=5.0, max =7.5. A boxplot is created. Which feature is consistent with the summary statistics?
- The box extends from 2.0 to 7.5, and the whiskers extend from 3.5 to 5.0.
- The median line is located at 4.2 within a box from 3.5 to 5.0. (correct answer)
- The interquartile range is 7.5−2.0=5.5 miles.
- Because the maximum is 7.5, 7.5 must be an outlier and not part of the whisker.
- The left whisker extends from 5.0 down to 3.5.
Explanation: This question tests recognition of correct boxplot features from given summary statistics. In a boxplot, the box spans from Q₁ (3.5) to Q₃ (5.0), with the median line drawn at 4.2 within this box. The whiskers extend from the box to the minimum (2.0) and maximum (7.5) values. Choice B correctly states that the median line is at 4.2 within a box from 3.5 to 5.0. The distractors reveal common misunderstandings: the box doesn't extend to the extremes, the IQR is 5.0-3.5=1.5 miles (not 5.5), values in a five-number summary are not outliers, and whiskers extend outward from the box (not between quartiles). A key principle: the box always contains the middle 50% of the data.
Question 16
A city planner summarizes commute times (in minutes) for 70 randomly selected workers. The five-number summary is: minimum 9, Q1=18, median 27, Q3=44, maximum 90. A boxplot is created from these values. Which feature is consistent with the summary statistics?
- The IQR is 44−18=26 minutes. (correct answer)
- The median is at 18 minutes.
- The left whisker ends at 44 minutes.
- The box extends from 9 to 90 minutes.
- The range is 44−18=26 minutes.
Explanation: This question requires calculating boxplot features from given summary statistics. With the five-number summary (min=9, Q1=18, median=27, Q3=44, max=90), we can determine each component. The IQR equals Q3-Q1 = 44-18 = 26 minutes, which matches choice A. The median is at 27 minutes, not 18. The left whisker extends from the minimum (9) to Q1 (18), not ending at 44. The box extends from Q1 to Q3 (18 to 44), not from minimum to maximum. The range is max-min = 90-9 = 81 minutes, not 26. Remember that IQR measures the spread of the middle 50% of data and is represented by the length of the box in a boxplot.
Question 17
A delivery company summarizes the number of packages delivered per route for 45 routes last Friday. The five-number summary is: minimum 18, Q1=30, median 41, Q3=55, maximum 60. A boxplot is constructed from these statistics. Which feature is consistent with the summary statistics?
- The left whisker has length 30−18=12 packages. (correct answer)
- The box has length 60−18=42 packages.
- The median is at 55 packages.
- The right whisker ends at 55 packages.
- The IQR equals 41−30=11 packages.
Explanation: This question requires identifying correct boxplot features from given summary statistics. With the five-number summary (min=18, Q1=30, median=41, Q3=55, max=60), we can determine each boxplot component. The left whisker extends from the minimum (18) to Q1 (30), giving it a length of 30-18 = 12 packages, which matches choice A. The box itself extends from Q1 to Q3 (30 to 55), not from the minimum to maximum. The median line is at 41 packages, not 55. The right whisker extends from Q3 (55) to the maximum (60). The IQR equals Q3-Q1 = 55-30 = 25 packages, not 11. When reading boxplots, remember that whiskers connect the box to the extreme values, while the box itself spans only the middle 50% of the data.
Question 18
A car dealership summarized the prices (in thousands of dollars) of 20 used cars currently in stock. The five-number summary is: min =8, Q1=11, median =14, Q3=18, max =29. A boxplot is drawn from these statistics. Which feature is consistent with the summary statistics?
- The median line is drawn at 18.
- The right whisker extends from 18 to 29. (correct answer)
- The IQR equals 29−8=21.
- The box extends from 8 to 29.
- The left whisker extends from 8 to 14.
Explanation: This question evaluates knowledge of summary statistics representations, particularly ensuring boxplot features match the data. The right whisker extends from Q3 (18 thousand dollars) to the max (29), as described in choice B, which is consistent. The box is from Q1 (11) to Q3 (18), with median at 14, and left whisker from min (8) to Q1. Distractors like choice C confuse IQR (7) with range (21), and choice E extends the left whisker to the median instead of Q1. A mini-lesson on reading boxplots: focus on the five-number summary to understand center (median), spread (IQR and range), and shape (whisker asymmetry), which here shows a longer right whisker suggesting right-skewed prices.
Question 19
A gym recorded the number of minutes 40 members spent on a treadmill during one visit. The five-number summary (in minutes) is: min =12, Q1=20, median =28, Q3=35, max =58. A boxplot is drawn using the standard rule (whiskers extend to the min and max, with no outliers marked). Which feature is consistent with the summary statistics?
- The box extends from 12 to 58 minutes.
- The left whisker extends from 12 to 20 minutes. (correct answer)
- The median is located at 35 minutes.
- The interquartile range is 46 minutes.
- The right whisker extends from 35 to 58 minutes.
Explanation: This question assesses the skill of interpreting graphical representations of summary statistics, particularly boxplots constructed from a five-number summary. In a standard boxplot without outliers, the box spans from the first quartile (Q1 = 20 minutes) to the third quartile (Q3 = 35 minutes), with the median line at 28 minutes, while the left whisker extends from the minimum (12 minutes) to Q1 (20 minutes) and the right whisker from Q3 to the maximum (58 minutes). Choice B correctly describes the left whisker extending from 12 to 20 minutes, which matches the summary statistics. A common distractor, like choice A, mistakenly describes the box as spanning the entire range from min to max, while choice D confuses the interquartile range (IQR = Q3 - Q1 = 15 minutes) with the full range. To read a boxplot effectively, identify the five key points: min, Q1, median, Q3, and max, which divide the data into quarters and highlight the distribution's spread and central tendency. Understanding these features helps in recognizing skewness, such as the longer right whisker here indicating potential right-skewness.
Question 20
A librarian recorded the number of books checked out by 60 patrons in one week. The five-number summary (books) is: min =0, Q1=1, median =2, Q3=4, max =15. A standard boxplot is drawn. Which feature is consistent with the summary statistics?
- The right whisker extends from 4 to 15 books. (correct answer)
- The left whisker extends from 0 to 2 books.
- The box extends from 0 to 15 books.
- The IQR is 15−0=15 books.
- The median is at Q1=1 book.
Explanation: This question assesses understanding of summary statistics through boxplots, emphasizing correct identification of features. The right whisker extends from Q3 (4 books) to the max (15 books), confirming choice A as consistent with the five-number summary. The box spans Q1 (1) to Q3 (4), with median at 2, and left whisker from min (0) to Q1. Distractors include choice D, confusing IQR (3 books) with range (15), and choice B, incorrectly extending the left whisker to the median. A mini-lesson on boxplots: they divide data into quartiles, with the box showing IQR for spread, median for location, and whiskers for overall range, useful for visualizing skewness, evident here by the extended right whisker indicating right-skewness.