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← Data & Patterns III: Running a Small Survey

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Lesson 7 of 8

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Here are the five rules, word for word. Use the table if you get stuck.

Running a small survey — the five rules
IdeaThe rule
A good questionA good question gets answers you can put side by side. Answers in many different forms cannot be compared.
Same way every timeUse one method, the same way, for every person. A missing step can spoil many rows at once.
The meanThe mean is the sum divided by the count. It is each value's share when the total is shared equally.
Which chartDraw a chart when the question compares groups. For one row, read the table.
What it showsA conclusion is only as wide as the rows behind it. A tiny group or a missed person makes it a hint.

Twelve students are asked, "Tell us about your morning." What does a tally of the answers give?

  • Twelve piles of one, so nothing to compare
  • A few piles, sorted by the main words
  • Nothing, because a tally takes only numbers

Student 1 writes "8 minutes". Student 2 writes "eight minutes". Both take 8 minutes. What does the tally do?

  • Puts them in one pile, because 8 and eight are the same
  • Makes two piles, because the written answers differ
  • Waits until someone fixes the spelling

Which question gets answers you can put side by side?

  • Tell us about your trip to school.
  • How is the traffic these days?
  • How many minutes from home to the school gate?

A survey method is ask, wait, write. The "wait" step is skipped. What happens to the row of a student who thinks first?

  • It is filled in, but late
  • It comes back blank
  • It is filled with the mean

The "ask" step is left out. How many of the 12 rows are filled?

  • None, because nothing was asked
  • 11, because one student speaks up
  • 12, because you can write anyway

A blank row is filled with a guess. Why is that worse than a blank?

  • Guesses are always too high
  • It changes the number of rows
  • The guess looks just like a real answer

Eight answers add up to 56 minutes. What is the mean?

  • 7 minutes, because 56 ÷ 8 = 7
  • 8 minutes, because there were 8 students
  • 48 minutes, because 56 − 8 = 48

Twelve answers add up to 129 minutes. What is the mean?

  • 11 minutes, rounded up
  • 10.75 minutes, because 129 ÷ 12 = 10.75
  • 9 minutes, because 129 − 120 = 9

The mean is 10.75, but 10 of the 12 trips are shorter. Why?

  • One very long trip, 45 minutes, pulled the mean up
  • The mean was worked out wrongly
  • Ten students gave wrong answers

"Is Student 3's trip longer than Student 7's?" Table or chart?

  • Table, because two rows are quicker to read than to draw
  • Chart, because charts are always clearer
  • Neither, find the mean first

"How do most students come: on foot, by cycle or by bus?" Table or chart?

  • Table, because the answers are in one column
  • Neither, find the mean first
  • Chart, because 3 groups can be compared at a glance

Eleven rows say 15 minutes or less. One row says 45. Does the data show "everybody takes 15 minutes or less"?

  • Yes, because eleven rows agree
  • No, because one row that disagrees ends a claim about everybody
  • Only if the 45 is checked again

10 of 12 trips are under 11 minutes. Does the data show "most of the 12 take under 11 minutes"?

  • Yes, because 10 of 12 is most
  • No, because two rows disagree
  • No, because "most" can only ever be a hint

Only 2 rows are from the far side. Both took longer. What may the report say?

  • Far-side students take longer, full stop
  • Nothing at all
  • The data hints that far-side students take longer, from only 2 rows

Four far-side students were never asked. Someone says, "Ask the gate students again." Does that fix it?

  • Yes, because more answers are always better
  • No, because the four missed students are still missed
  • Yes, if the gate students answer faster

Next, a program learns from rows like these. Open AI Literacy III: How Machines Learn.

Reveal every answer to finish this lesson.