Outliers, and choosing the best measure of center and spread

Answer Key - Grade 9 Math Worksheet - Building Confidence

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

1. 1.

   Ari timed bus rides to school. Q1 is 18 minutes and Q3 is 26 minutes. What is the upper fence, Q3 + 1.5 × IQR?

   38
2. 2.

   Bo recorded minutes spent reading after school. Q1 is 20 minutes and Q3 is 34 minutes. What is the upper fence, Q3 + 1.5 × IQR?

   55
3. 3.

   Jun measured bean plants in the class garden. Q1 is 28 cm and Q3 is 36 cm. What is the lower fence, Q1 − 1.5 × IQR?

   16
4. 4.

   Kira listed the class's spelling quiz scores out of 50. Q1 is 32 points and Q3 is 42 points. What is the lower fence, Q1 − 1.5 × IQR?

   17
5. 5.

   Luz measured paper airplane flights (one took a nosedive). Q1 is 11 meters and Q3 is 16 meters. What is the lower fence, Q1 − 1.5 × IQR?

   3.5
6. 6.

   Noah measured twelve sunflower seedlings in cm. Q1 is 17 and Q3 is 22, so the fences are 9.5 and 29.5. Which heights are outliers?

   • Only 26
   • 4, 15, 24 and 26
   • No value is an outlier
   • Only 4
7. 7.

   Pia timed twelve bus rides home in minutes. Q1 is 16 and Q3 is 21, so the fences are 8.5 and 28.5. Which rides are outliers?

   • Only 33
   • 3 and 33
   • 3, 14, 23 and 33
   • No value is an outlier
8. 8.

   Tala timed nine waits in the lunch line. The dots have a long tail to the right. The mean is 8 minutes and the median is 6 minutes. Which center describes a typical wait better?

   • The median, 6, because the long tail pulls the mean up
   • The mean, 8, because it uses every wait and the tail is not a problem
   • The range, 15, because it covers every wait
9. 9.

   Zee listed nine spelling scores out of 10. The dots have a long tail to the left. The mean is 8 and the median is 9. Which center describes a typical score better?

   • The range, 7, because it covers every score
   • The mean, 8, because it uses every score and the tail is not a problem
   • The median, 9, because the long tail pulls the mean down
10. 10.

    Bo timed nine bike rides in minutes. The dots balance around the middle, with no outliers. The mean is 27 minutes and the median is 28 minutes. Which center describes a typical ride better?

    • The mean, 27, because the dots balance with no outliers
    • The median, 28, because an outlier pulls the mean
    • The range, 13, because it covers every ride