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.

   Esme counted jump rope skips in one minute. Q1 is 46 skips and Q3 is 61 skips. What is the upper fence, Q3 + 1.5 × IQR?

   83.5
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.

   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 4
   • No value is an outlier
   • 4, 15, 24 and 26
   • Only 26
6. 6.

   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?

   • 3, 14, 23 and 33
   • Only 33
   • No value is an outlier
   • 3 and 33
7. 7.

   Ren listed twelve quiz scores out of 20. Q1 is 13 and Q3 is 17, so the fences are 7 and 23. Which scores are outliers?

   • 9, 12, 18 and 20
   • No value is an outlier
   • Only 20
8. 8.

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

   Ari measured eight sunflowers in cm. The dots balance around the middle, with no outliers. The mean is 150 cm and the median is 151 cm. Which center describes a typical height better?

   • The range, 14, because it covers every height
   • The mean, 150, because the dots balance with no outliers
   • The median, 151, because an outlier pulls the mean, so the median is safer
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 median, 28, because an outlier pulls the mean
    • The mean, 27, because the dots balance with no outliers
    • The range, 13, because it covers every ride