Outliers, and choosing the best measure of center and spread

Answer Key - Grade 9 Math Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   Jun recorded twelve library visits in minutes. The values are not in order. How many of them are outliers by the 1.5 × IQR rule?

   2
2. 2.

   Kira counted jump rope skips in a minute for twelve classmates. The values are not in order. How many of them are outliers by the 1.5 × IQR rule?

   2
3. 3.

   Milo listed the pages in twelve library books. The values are not in order. How many of them are outliers by the 1.5 × IQR rule?

   2
4. 4.

   Noah timed eight maze runs in minutes. The run of 39 minutes is an outlier. When it is removed, how much more does the mean drop than the median?

   2.5
5. 5.

   Ren counted skips in 30 seconds for eight classmates (one rope tangled). The count of 7 skips is an outlier. When it is removed, how much more does the mean rise than the median?

   2.25
6. 6.

   Tala recorded eight quiz scores out of 40. The score of 6 points is an outlier. When it is removed, how much more does the mean rise than the median?

   2.625
7. 7.

   Zee timed a maze for two clubs of eight. Group A has one outlier, 34. Which statement compares the two groups fairly?

   • B's typical time is longer (medians 14.5 and 13.5), and A's middle half is less spread (IQRs 3 and 6).
   • A's typical time is longer (medians 13.5 and 14.5), and B's middle half is less spread (IQRs 6 and 3).
   • A's typical time is longer (means 15.625 and 14.625), and A's middle half is less spread (IQRs 3 and 6).
   • B's typical time is longer (medians 14.5 and 13.5), and A is more spread out (ranges 24 and 10).
8. 8.

   Ari measured bean plants from two windowsills, eight each, in cm. Group A has one outlier, 47. Which statement compares the two groups fairly?

   • B's typical height is taller (medians 26 and 24.5), and A is more spread out (ranges 27 and 14).
   • B's typical height is taller (medians 26 and 24.5), and A's middle half is less spread (IQRs 3 and 8).
   • A's typical height is taller (means 26.75 and 26), and A's middle half is less spread (IQRs 3 and 8).
   • A's typical height is taller (medians 24.5 and 26), and B's middle half is less spread (IQRs 8 and 3).
9. 9.

   Bo recorded paper airplane flights for two teams of eight, in meters. Group A has one outlier, 24. Which statement compares the two groups fairly?

   • B's typical flight is longer (medians 9.5 and 8.5), and A's middle half is less spread (IQRs 3 and 6).
   • B's typical flight is longer (medians 9.5 and 8.5), and A is more spread out (ranges 19 and 10).
   • A's typical flight is longer (means 10 and 9.125), and A's middle half is less spread (IQRs 3 and 6).
   • A's typical flight is longer (medians 8.5 and 9.5), and B's middle half is less spread (IQRs 6 and 3).
10. 10.

    Esme counted pages read in a day by two reading groups of eight. Group A has one outlier, 52. Which statement compares the two groups fairly?

    • B's typical count is higher (medians 21.5 and 20.5), and A is more spread out (ranges 38 and 16).
    • B's typical count is higher (medians 21.5 and 20.5), and A's middle half is less spread (IQRs 4 and 9).
    • A's typical count is higher (medians 20.5 and 21.5), and B's middle half is less spread (IQRs 9 and 4).
    • A's typical count is higher (means 23.375 and 20.625), and A's middle half is less spread (IQRs 4 and 9).