Presentation of quantitative data

Question 1

Tables

Answer 1

Raw scores displayed in columns and rows.
A summary paragraph beneath the table explains the findings and draws conclusions.

Question 2

Bar charts

Answer 2

Categories (discrete data) are usually placed along the x-axis and frequency on the y-axis (or can be reversed).
The heights of each column represents the frequency of that item.

Question 3

Histograms

Answer 3

Bars touch each other (in a bar chart they don’t) - data is continuous rather than discrete. There is a true zero.

Question 4

Scattergrams

Answer 4

Used for correlation analysis. Each dot represents one pair of related data. Illustrates strength and direction of correlation.
The data on both axes must be continuous.

Question 5

Normal distribution

Answer 5

Symmetrical, bell-shaped curve. Most items are in the middle area of the curve with very few at the extreme ends.
The mean, median and mode all occupy the same mid-point of the curve.

Question 6

Skewed distribution

Answer 6

Distributions that lean to one side or the other because most items are either at the lower or upper end of the distribution.

Question 7

Negative skew

Answer 7

Most of the distribution is concentrated towards the right of the graph, resulting in a long tail on the left.
E.g. a very easy test in which most people get high marks would produce a negative skew.
The mode is the highest point of the peak, the median comes next, and the mean is dragged across to the left (if scores are arranged from lowest to highest).

Question 8

Positive skew

Answer 8

Most of the distribution is concentrated towards the left of the graph, resulting in a long tail on the right.
E.g. a very difficult test in which most people get low marks would produce a positive skew.
The mode is the highest point of the peak, the median comes next, and the mean is dragged across to the right (if scores are arranged from lowest to highest).