Graphs

Question 1

Identify three features of a normal distribution (3 marks)

Answer 1

• Frequency of measurements forms a bell shaped curve
• Most people are located in the middle area of the curve with very few people at the extreme ends.
• The mean, median and mode all occupy the same mid-point of the curve as there are no extreme values skewing the data
• The tails of the curve never touch the horizontal x-axis as more extreme values are theoretically possible.

Question 2

Explain the difference between a positive and a negative skew (3 marks)

Answer 2

A positive skew is where most of the distribution is concentrated towards the left of the graph, resulting in a long tail on the right.
A negative skew is where most of the distribution is concentrated towards the right of the graph, resulting in a long tail on the left.
Means are skewed as they are affected by extreme values.