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Grade 9 · Math · Algebra 1

9th grade Outliers, and choosing the best measure of center and spread worksheet

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Outliers, and choosing the best measure of center and spread

Grade 9 Math Worksheet

NameDate

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

  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?

  2. 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?

  3. 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?

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

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

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

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

  6. Ren listed twelve science quiz scores out of 50. Which scores are outliers by the 1.5 × IQR rule?

    • 31, 35, 45 and 50
    • No value is an outlier
    • Only 50

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

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

  8. Ari measured ten pumpkin vines in meters. Which pair of measures should Ari 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

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

  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 IQR
    • The median and the standard deviation
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9th grade Outliers, and choosing the best measure of center and spread worksheet – printable
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About this worksheet

Outliers, and choosing the best measure of center and spread. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can find the fences Q1 − 1.5 × IQR and Q3 + 1.5 × IQR and name the outliers.
  • I can say whether the mean or the median shows a typical value, from the shape of the dots.
  • I can compare two groups fairly when one of them has an outlier.

Standard: S-ID.A.2, S-ID.A.3

Words to know

quartiles (Q1, Q3): The middles of the lower half and the upper half of the ordered values.

IQR: Q3 − Q1: how wide the middle half of the dots is.

fence: The line 1.5 IQRs past Q1 or Q3. A dot past a fence is an outlier.

outlier: A value past a fence: far from the rest of the dots.

skewed, tail: Most dots bunch up, and a few stretch out to one side.

symmetric: The dots balance around the middle, about the same on each side.

standard deviation (SD): A spread measure built from gaps to the mean; topic 64 shows how to find it.

Common mistakes

Your child stepped one IQR past the box instead of 1.5 IQRs.

Your child measured the fence from the wrong end of the box.

Your child found how far past the box the fence is, but stopped before placing the fence.

What to say

Ask: what do we multiply the IQR by before we add or subtract it?

Ask: which end of the box is closer to the high values, and which to the low ones?

Ask: where does that distance start?

Questions parents ask

What is the most common mistake with outliers, and choosing the best measure of center and spread?

Your child stepped one IQR past the box instead of 1.5 IQRs.

How can I help my child with outliers, and choosing the best measure of center and spread?

Ask: what do we multiply the IQR by before we add or subtract it?

Are these 9th grade math worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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