Exploratory Analysis and an Honest Chart · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Look first, then chart it honestly

Computing · Data & Databases · ages 21-22
Name ______________________   Date ____________

  1. You want to study how two number variables, like hours of practice and quiz score, move together. What should you do first?

    • Make a scatterplot of the two variables
    • Calculate the correlation coefficient right away
    • Fit a regression line through the data
    • Compute the mean of each variable and stop

  2. Which chart compares two sets of data?

    • Bar chart
    • Pie chart of one set
    • A table of passwords

  3. Bar charts should start their axis at zero.

    Circle one:   True   False

  4. What do you make before computing correlation?

    • A regression line at once
    • A scatterplot of the two variables
    • The mean and then stop

  5. You want to compare the distribution of commute times for cyclists and for drivers. Which display shows the comparison best?

    • Side-by-side boxplots of the two groups
    • A pie chart of the group sizes
    • One scatterplot of time against time
    • A single bar of the overall average

  6. Which of these is NOT a way to display categorical data?

    • Histogram
    • Bar graph
    • Pie chart
    • Frequency table

  7. For which pair of variables would it make sense to calculate a correlation?

    • The height and weight of each student in a class
    • Each student's favourite colour and their name
    • Each student's shoe size and their lucky number
    • Each student's locker number and their grade level

  8. A frequency table says 0 goals happened 2 times, 1 goal happened 3 times, 2 goals happened 4 times, and 3 goals happened 1 time. What is the mean number of goals per game? Round to one decimal place.

    Answer: ______________

  9. An outlier traces to a broken sensor. What is the honest move?

    • Keep it to protect the average
    • Copy it into every row
    • Remove it and write down why

  10. A cut axis made sales look tripled. What did the original make readers believe?

    • That sales happened on the moon
    • That bars taste better tall
    • That growth was huge when it was tiny
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Look first, then chart it honestly W1-mt_Jpb78Z6Ytu-s1

  1. Make a scatterplot of the two variables · Before any calculation, plot the data. A scatterplot shows the shape of the relationship and any outliers that would make a number misleading.
  2. Bar chart · Bars exist for listing differences and comparing similar sets.
  3. True · Starting at zero keeps small gaps looking small.
  4. A scatterplot of the two variables · A plot shows the shape that a bare number would hide.
  5. Side-by-side boxplots of the two groups · Side-by-side boxplots put the shape, centre, and spread of each group in one view, which a pie chart, an average, or a plot of a variable against itself cannot do.
  6. Histogram · A histogram bins a quantitative variable into number ranges. Categories like breeds or colours have no order or width, so they belong in bars, pies, or tables.
  7. The height and weight of each student in a class · Correlation is only for two quantitative variables measured on the same cases. Names, colours, and locker numbers are labels, not measurements.
  8. 1.4 · Multiply each value by its frequency, add the products, and divide by the total count: (0*2 + 1*3 + 2*4 + 3*1) / 10 = 1.4 goals per game.
  9. Remove it and write down why · A proven error may go, but only with the reason on record.
  10. That growth was huge when it was tiny · Stretched gaps sell a tiny rise as a boom, which the redraw exposes.
Worksheet · LightMySky