Chapter 3

Question 1

What don’t intervals need to be?

Answer 1

Of equal class width. Use narrower intervals where the data are grouped together and wider intervals where the data are spread out

Question 2

What can pie charts be used to show?

Answer 2

Continuos data. The area of each sector represents the frequency for that class interval. Other than this the chart is drawn in the same way as discrete data.

Question 3

If there are not too many observations what can they be treated as in a stem and leafy diagram?

Answer 3

Treated as individual numbers. The stem shows the first digit(s) of the numbers and the leafs show the last digit

Question 4

What is cumulative frequency?

Answer 4

A running total of frequencies

Question 5

What can cumulative frequency diagrams be used for?

Answer 5

Used to estimate or predict other values

Question 6

What is a histogram?

Answer 6

Similar to a bar chart but, because the data are continuos, there are no gaps between the bats

Question 7

What does a frequencies polygon join?

Answer 7

Joins the mid-points of the top of the bars with straight lines

Question 8

What does a histogram show?

Answer 8

Shows how the data are distributed across the class intervals

Question 9

what can distributions be?

Answer 9

Symmetrical
Have a positive skew
Have a negative skew

Question 10

To draw a histogram for unequal class intervals what do you need to do?

Answer 10

You need to adjust the heights of the bars so the area is proportional to the frequency

Question 11

How can you find the frequency density?

Answer 11

By dividing the frequency by the class width

Question 12

What are the frequency density and the width of the class interval used to work out?

Answer 12

Work out the frequency of each class interval in a histogram 
Frequency = frequency density ✖️ class width

Question 13

Describe Population pyramids

Answer 13

Population pyramids looks similar to back to back histograms. They make it easy to compare aspects of a population, often by gender.
They usually have class sizes, and therefore bars, the same width

Question 14

Chloropleth maps

Answer 14

A Chloropleth map is used to classify regions of a geographical area. Regions are shaded with an increasing depth of colour. A key shows what each shade represents

Question 15

What can continuos data be sorted into?

Answer 15

A frequency table. The class intervals must not have gaps in between them or overlap each other.
All possible values that round to the same number must fit into the same class interval