Grade 8 Data Handling Quiz 3 draws its questions at random from 24 questions across these topics:
A few of the question types, with full solutions, so you know what to expect.
Types of data. Which one of these data sets can you calculate a mean for?
Answer: Shoe sizes of 20 learners
A mean needs values you can add up and divide.
Shoe size is numerical - it is measured.
The other three are categorical - they are names, not numbers.
Tip: There is no such thing as an average favourite sport. For categorical data only the MODE applies.
Types of data. Twenty learners named their favourite sport. Nine said soccer, which was more than any other. Which measure describes this data?
Answer: The mode
The data is categorical, so it cannot be added or ordered meaningfully.
Tip: Mode is the only measure of central tendency that works on categorical data.
Collecting data. Why is "Is your family big?" a poor questionnaire question?
Answer: "Big" means different things to different people
A good question must be clear, answerable, and have only one meaning.
Two learners from identical households could answer differently, so the data measures opinion, not fact.
Tip: "How many people live in your home?" fixes it - one clear meaning, one countable answer.
Tally marks. How is the number 5 recorded in tally marks?
Answer: Four strokes with the fifth struck diagonally across them
Tallies are grouped in fives so a long list can be counted at a glance.
Tip: That gate of five is what stops you losing your place and counting the same item twice.
Frequency tables. In a frequency table the frequencies are 2, 6, 4, 2 and 1. The data set had 15 values. What does this tell you?
Answer: The table is correct, because the frequencies add up to 15
\(2 + 6 + 4 + 2 + 1 = 15\)
This matches the number of values collected.
Tip: Always add your frequencies. If the total does not match, you have miscounted - and you have caught it yourself.