Numerical summaries (mean, median, variance, sd, IQR). Bivariate data: correlation, two-way tables

Question 1

Mean μ

Answer 1

Average of all data points.

Add all numbers together then divide by the total number of numbers.

Question 2

Median

Answer 2

The centre number in the ordered sequence of data points.

Question 3

Mode

Answer 3

The number that occurs the most in a data set.

Question 4

Standard deviation σ

Answer 4

How measures are spread out from the mean.
Low σ means numbers are close to the mean
High σ means numbers are spread out from the mean.

Question 5

Variance σ^2

Answer 5

Distance each number is from the mean.

Question 6

Range

Answer 6

Difference between highest and lowest values.

max - min = range

Question 7

Inter quartile range

Answer 7

Middle 50% of the data.

Q3 - Q1 = IQR

Question 8

Correlation coefficient r

Answer 8

r = -1 : as y decreases, x increases - negative linear 
r = 0 : no linear model - no association 
r = 1 : as x increases so does y - positive linear

Question 9

How to best represent data for 1 qualitative and 1 quantitative variable?

Answer 9

Side-by-side boxplot

Question 10

How to best represent data for 2 quantitative variables?

Answer 10

Scatterplot

Question 11

Bivariate data

Answer 11

For each x data point there is a corresponding y data point