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Grade 8 · lesson 1 of 4

Compare a Mean with Individual Values

Add the values and divide by the number of supplied values.

About 18 minutes, plus any extended practice

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Supplied materials

  • Paper and pencil; answers may also be spoken or typed.
  • All cases, labels, numbers and rules are supplied on this page. No real account, private information or purchase is needed.

Learn the idea

A mean is the total divided by the number of values. It summarizes a dataset without preserving every observation. In a small dataset an unusually large value can pull the mean upward. Use the original list as well as the summary before making a statement about typical observations.

Add the values and divide by the number of supplied values. The mean need not equal a value that any item actually has.

Use this supplied case: Paper Python 3 expression: sum([2,4,6])/len([2,4,6]). What value results? The task is to connect the given information to the computing idea. Write a short evidence trail so another learner can reproduce your choice. The simplified case describes the stated model, not every real system.

  1. Represent the supplied worked case with a labeled drawing, table or short trace.
  2. Add the values and divide by the number of supplied values.
  3. Explain why the worked answer fits and why one alternative does not.
  4. Try the new check and practice cases; revisit the stated rule if your evidence does not match.
Worked example

See the method in action

Paper Python 3 expression: sum([2, 4, 6])/len([2, 4, 6]). What value results? The supported answer is 4.0. Tracing the expression under Python 3 rules gives 4.0. Add the values and divide by the number of supplied values. The mean need not equal a value that any item actually has. A mean is the total divided by the number of values.

Your turn

Check your reasoning

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Helpful tips
  • Add the values and divide by the number of supplied values.
  • The mean need not equal a value that any item actually has.
Paper Python 3 expression: sum([3,5,7])/len([3,5,7]). What value results?

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See the answer and explanation

5.0

The numerator evaluates to 15 and the denominator to 3. Divide 15 by 3 to obtain 5.0; keep every supplied observation in the denominator. Add the values and divide by the number of supplied values.

Take it further

New list[2, 3, 10]has mean 15/3=5 and median 3. Explain how the high value affects the mean; the mean is not every observation.

Nothing here is saved to an account or sent to a teacher. The answer download includes your current choice and any checked feedback. It does not include choices from the separate More practice section. Download that section separately.

More practice: try new cases

Choose an answer for each problem. Explain your method on paper, then use the feedback to decide what to revisit.

More practice: try new cases
1. Paper Python 3 expression: sum([1,2,9])/len([1,2,9]). What value results?
Need a hint?
  • Add the values and divide by the number of supplied values.
  • The mean need not equal a value that any item actually has.
2. Paper Python 3 expression: sum([4,6,8,10])/len([4,6,8,10]). What value results?
Need a hint?
  • Add the values and divide by the number of supplied values.
  • The mean need not equal a value that any item actually has.
3. Paper Python 3 expression: sum([2,2,8])/len([2,2,8]). What value results?
Need a hint?
  • Add the values and divide by the number of supplied values.
  • The mean need not equal a value that any item actually has.

Your choices are temporary. Feedback appears after you check all the answers.

Nothing here is saved to an account or sent to a teacher. Keep your own notes or download them before leaving. The score describes these questions; it does not certify subject mastery.

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These LifeStarter passages, scenarios and exercises are authored for this Academy with AI assistance and review. External resources keep their publishers’ terms. A grade label suggests a starting level; it does not establish alignment with your school’s complete requirements.