Outliers, and choosing the best measure of center and spread

Answer Key - Grade 9 Math Worksheet

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

1. 1.

   Esme recorded twelve homework times in minutes. Use Q1 and Q3 (the middles of the two halves). What is the upper fence for outliers by the 1.5 × IQR rule?

   50
2. 2.

   Jun measured twelve bean plants in cm. Use Q1 and Q3 (the middles of the two halves). What is the upper fence for outliers by the 1.5 × IQR rule?

   30
3. 3.

   Kira timed twelve walks to school in minutes. Use Q1 and Q3 (the middles of the two halves). What is the lower fence for outliers by the 1.5 × IQR rule?

   4.5
4. 4.

   Luz counted the pages twelve classmates read in a day. Use Q1 and Q3 (the middles of the two halves). What is the lower fence for outliers by the 1.5 × IQR rule?

   2.5
5. 5.

   Milo timed twelve drawings in minutes. Which times are outliers by the 1.5 × IQR rule?

   • 14, 16, 31 and 36
   • No value is an outlier
   • 31 and 36
   • Only 36
6. 6.

   Noah measured twelve tomato plants in cm. Which heights are outliers by the 1.5 × IQR rule?

   • Only 9
   • 9 and 15
   • No value is an outlier
   • Only 31
7. 7.

   Pia recorded twelve morning reading times in minutes. Which times are outliers by the 1.5 × IQR rule?

   • No value is an outlier
   • 2 and 38
   • Only 38
   • 2, 15, 27 and 38
8. 8.

   Tala counted jumping jacks in one minute for twelve classmates. Which counts are outliers by the 1.5 × IQR rule?

   • 18, 34, 49 and 52
   • No value is an outlier
   • Only 52
   • Only 18
9. 9.

   Zee timed ten trips to school in minutes. Which pair of measures should Zee use to describe the center and the spread?

   • The median and the IQR
   • The mean and the standard deviation
   • The median and the standard deviation
10. 10.

    Ari measured ten pumpkin vines in meters. Which pair of measures should Ari use to describe the center and the spread?

    • The median and the standard deviation
    • The mean and the standard deviation
    • The median and the IQR