Skewed Distributions

Question 1

Normal distribution?

Answer 1

Mean = median = mode

Question 2

What is the mean, median and mode?

Answer 2

Ways to calculate the average of a set of data, or a measure of central tendency.

Question 3

How to calculate the mean?

Answer 3

Add all the values together and divide by the number of values in the set –> average of the set of data.

Question 4

How to calculate the median?

Answer 4

The middle value in a set of values when arranged in order.

The median is not affected by extreme values.

Question 5

How to calculate the mode?

Answer 5

The value that occurs most often in a set of values.

Question 6

Positively skewed distribution?

Answer 6

Mean > median > mode

Question 7

Negatively skewed distribution?

Answer 7

Mean < median < mode

To remember the above note how they are in alphabetical order, think positive going forward with ‘>’, whilst negative going backwards ‘<’

Question 8

Properties of normal distribution?

Answer 8

1) symmetrical i.e. Mean = mode = median

2) 68.3% of values lie within 1 SD of the mean

3) 95.4% of values lie within 2 SD of the mean

4) 99.7% of values lie within 3 SD of the mean

Question 9

Define standard deviation

Answer 9

A measure of how much dispersion exists from the mean

SD = square root (variance)