Variability and sampling 2

Question 1

2. Systematic Sampling
   * Another method of sampling from the population with a…
   * Define the … item
   * …= population size/sample size
   * Pick every … item

Example:
You want to obtain a sample of 500 individuals from a town of 10,000
people using systematic sampling.
k= population size/sample size
k= 10,000/500
k= 20
e.g. 20 th, 40 th, 60 th, 80 th, ..

Answer 1

2. Systematic Sampling
   * Another method of sampling from the population with a defined sample size number
   * Define the kth item
   * k= population size/sample size
   * Pick every kth item

Question 2

3. Stratified Random Sampling
   * Population is too …
   * Divide the population into …
   * Size
   * Colour
   * Randomly select from each …
   * Proportionally select…
4. Cluster Sampling
   * Divide the population into …
   * Randomly select …

Answer 2

3. Stratified Random Sampling
   * Population is too large
   * Divide the population into “strata” Characteristics
   * Size
   * Colour
   * Randomly select from each strata
   * Proportionally select the number
4. Cluster Sampling
   * Divide the population into “clusters”
   * Randomly select the cluster to be used

Question 3

Frequency Distributions

Answer 3

In statistics, a frequency distribution is a table that displays the frequency of various outcomes in a sample.

[1] Each entry in the table contains the frequency
or count of the occurrences of values within a particular group or interval, and in this way, the table summarizes the distribution of values in the sample.

Question 4

Question 5

Other types of distributions that are not normally
distributed

• … distribution (… law)
• Example of non-normal distribution
• Pareto distributions are common in:
• Creative fields
• Productivity
• Charitable donations
• Artistic works / talent
• Wealth / Income..

Answer 5

Other types of distributions that are not normally
distributed
* Pareto distribution (80 /20 law)
* Example of non-normal distribution
* Pareto distributions are common in:
* Creative fields
* Productivity
* Charitable donations
* Artistic works / talent
* Wealth / Income

Question 6

Data types influence the way your data will be
graphed!

why and when

Answer 6

changing it from discrete to continous

Question 7

Question 8

Bias: Definition -

negatively and positively skewed bias

Answer 8

Bias: Definition - To unevenly weight something

You might desire negatively skewed data when analyzing exam scores where most students perform well, or in situations where you expect a majority of values to cluster around a higher end, with a few outliers at the lower end.

Question 9

Confounding variability
* Makes trends or differences in the data…
* Signal to noise ratio (… vs …)
* Confounding variability increases with…
* Increases in … groups
* Is generally … to control for

• Examples of potential confounding variability in a
  cardiovascular study:
• Time of last meal, sleep quality, nutritional status, outside stress, inflammation, minor infections… etc.

Answer 9

Confounding variability
* Makes trends or differences in the data more difficult to see
* Signal to noise ratio (valuable information vs information)
* Confounding variability increases with diversity of subject pool
* Increases in heterogenous groups
* Is generally very difficult to control for

• Examples of potential confounding variability in a
  cardiovascular study:
• Time of last meal, sleep quality, nutritional status, outside stress,
  inflammation, minor infections… etc.

Question 10

What does confounding variability look like?

platykurtic

leptokurtic

Answer 10