courses › Probability & Statistics

Mean, median, and weighted averages.

In your head, jot if needed · no calculator why?

Learn first (about 3 minutes)

Opens at level 12.

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Builds on: Division (not open yet)

skills · practice stats

From rounds of this course only: box, review and trial answers are left out. Once a skill has 40 tries, it compares your first 20 tries with your last 20.

• Mean par 16 s not tried yet

  worked example

  What is the mean of 58, 94, 40, 84, 49?

  Answer: 65

  1. Add them: 58 + 94 + 40 + 84 + 49 = 325.
  2. Divide by how many there are, 5: 325 ÷ 5 = 65.

• Median par 13 s not tried yet

  worked example

  What is the median of 49, 44, 30, 25, 42, 24?

  Answer: 36

  1. Sort: 24, 25, 30, 42, 44, 49.
  2. With an even count, average the middle two: (30 + 42) ÷ 2 = 36.

• Score needed for a mean par 20 s not tried yet

  worked example

  Your first 2 test scores are 61 and 94. What score on test 3 makes the mean of all 3 scores exactly 80?

  Answer: 85

  1. You need a total of 3 × 80 = 240.
  2. You have 61 + 94 = 155, so you need 240 − 155 = 85.

• Weighted average par 25 s not tried yet

  worked example

  Your course grade is weighted: quizzes 60%, midterm 40%. You scored 63 on quizzes and 55 on the midterm. What is your overall grade?

  Answer: 59.8

  1. Multiply each score by its weight and add: 0.6 × 63 + 0.4 × 55
  2. = 37.8 + 22 = 59.8.

rest ladder

Win 3 of your last 4 rounds and the course rests. A win is 90% right, within 2× the round's par. Pass the review when it comes back and the next rest is longer.

1. 1 day
2. 3 days
3. 7 days
4. 14 days
5. 30 days
6. 60 days
7. mastered · every 90 days

your rounds

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