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

Introduction to Biostatistics > Numerical summaries (mean, median, variance, sd, IQR). Bivariate data: correlation, two-way tables > Flashcards

Flashcards in Numerical summaries (mean, median, variance, sd, IQR). Bivariate data: correlation, two-way tables Deck (11)
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1

Mean μ

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

2

Median

The centre number in the ordered sequence of data points.

3

Mode

The number that occurs the most in a data set.

4

Standard deviation σ

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.

5

Variance σ^2

Distance each number is from the mean.

6

Range

Difference between highest and lowest values.
max - min = range

7

Inter quartile range

Middle 50% of the data.
Q3 - Q1 = IQR

8

Correlation coefficient r

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

9

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

Side-by-side boxplot

10

How to best represent data for 2 quantitative variables?

Scatterplot

11

Bivariate data

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