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?

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

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

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

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

   • Only 52
   • No value is an outlier
   • Only 18
   • 18, 34, 49 and 52
8. 8.

   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
9. 9.

   Bo recorded ten violin practice times in minutes. Which pair of measures should Bo 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.

    Esme timed ten paper boats floating across a pond, in seconds. Which pair of measures should Esme use to describe the center and the spread?

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