Grade 8 Math · Data

Outliers and their effect on the mean

Identify an outlier in a small data set and determine how removing it changes the mean. Unlimited questions, five difficulty levels, and a full worked solution every time — free.

Practice this skill Curriculum: G8-D1.5, G8-D1.6

Try one

Here are the minutes 5 students spent on homework: 51, 15, 17, 18, 14. Which value is the outlier?

  • 14
  • 15
  • 51
  • 18

Answer: 51

See one solved, step by step

Homework minutes for 6 students: 48, 16, 18, 18, 20, 18. The value 48 is an outlier. What is the mean WITHOUT the outlier?

📘 Worked solution
118 + 16 + 18 + 20 + 18 = 90Add the 5 remaining values after removing the outlier.
290 / 5 = 18Divide by the number of values left. (With the outlier the mean was 23 — one extreme value dragged it by 5.)

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