Representation of data flashcards

Topic 2: Representation of data

Which parts of data representation are not required in 0479?

Drawing pictograms is not required, although reading a drawn pictogram is. Identifying outliers from a box-and-whisker diagram is not required.

How do you find the angle for a sector of a pie chart?

Angle = (frequency ÷ total) × 360°. Example: 18 out of 72 → 18/72 × 360° = 90°. Check the angles add to 360°.

How are the two circles of a comparative pie chart sized?

Their areas are in proportion to the totals, so the radii are in proportion to the square roots of the totals. Example: totals 50 and 200, first radius 2 cm → second radius 2 × √(200 ÷ 50) = 4 cm.

Pie chart or bar chart: what is each better at?

A pie chart shows each part as a proportion of the whole clearly. A bar chart makes it easier to compare exact values between categories.

What does a two-way table show?

It cross-tabulates two variables at once (for example travel method against gender). Be ready to read a single cell, a row total and a column total.

When is a Venn diagram the right representation?

When data falls into overlapping categories, for example students who cycle to school and also play a sport.

What is the advantage of a stem-and-leaf diagram?

It keeps every individual value visible while showing the shape. A back-to-back stem-and-leaf diagram compares two small data sets. It needs a key and becomes long for large data sets.

Which five values does a box-and-whisker diagram show, and what is it good for?

Minimum, lower quartile, median, upper quartile and maximum. It summarises spread and is good for comparing the middle 50% of two or more data sets.

What is the difference between a sectional bar chart and a multiple (dual) bar chart?

A sectional bar chart stacks the parts in one bar per group, showing the total and its make-up. A multiple bar chart puts separate bars side by side for comparison.

What does a "justify your choice of diagram" question need?

A reason tied to the data and the purpose, not just the name of the diagram. For example: a stem-and-leaf diagram keeps every value of this small set, which a grouped bar chart would lose.