Variability and sampling 2 Flashcards

Mastery

1
Q
  1. 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, ..

A
  1. 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
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2
Q
  1. Stratified Random Sampling
    * Population is too …
    * Divide the population into …
    * Size
    * Colour
    * Randomly select from each …
    * Proportionally select…
  2. Cluster Sampling
    * Divide the population into …
    * Randomly select …
A
  1. Stratified Random Sampling
    * Population is too large
    * Divide the population into “strata” Characteristics
    * Size
    * Colour
    * Randomly select from each strata
    * Proportionally select the number
  2. Cluster Sampling
    * Divide the population into “clusters”
    * Randomly select the cluster to be used
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3
Q

Frequency Distributions

A

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.

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4
Q
A
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5
Q

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..
A

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

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6
Q

Data types influence the way your data will be
graphed!

why and when

A

changing it from discrete to continous

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7
Q
A
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8
Q

Bias: Definition -

negatively and positively skewed bias

A

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.

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9
Q

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.
A

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.
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10
Q

What does confounding variability look like?

platykurtic

leptokurtic

A
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