Chapter 2 - Describing data: numerical

Question 1

Population variance

Answer 1

The sum of the squared differences between each observation

And the population mean divided by the population size

Question 2

Sample variance

Answer 2

The sum of the squared differences between each observation and the sample mean divided by the sample size

Question 3

Standard deviation

Answer 3

The population standard deviation with the square root

Question 4

Sample standard deviation

Answer 4

The sample variance with the square root

Question 5

How much data lies under 1 standard deviation from the mean?

Answer 5

68%

Question 6

How much data lies under 2 standard deviations from the mean?

Answer 6

95%

Question 7

Z - score

Answer 7

A standardised value that indicates the number of standard deviations a value is from the mean

Question 8

What does a z-score greater than zero indicate?

Answer 8

That the value is greater than the mean

Question 9

Covariance (Cov)

Answer 9

A measure of the inner relationship between two variables

A positive value indicates a direct or increasing linear relationship, and a negative value indicates a decreasing linear relationships

Question 10

Correlation coefficient

Answer 10

Computed by dividing the covariance by the product of the standard diatoms of the two variables