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Applied Probability and Statistics > Chapter One > Flashcards

Chapter One Flashcards

1
Q

What is statistics?

A

Statistics is the science of collecting, describing, and analyzing data.

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2
Q

True or false… statistics always involve some level of uncertainty?

A

True

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3
Q

What are cases?

A

Cases are people or objects that we gather data about (subjects = experimental units) (individuals = units / participants)

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4
Q

What are variables?

A

Variables are characteristics recorded for each case.

Ex. Gender, Class Year, or Height

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5
Q

What are categorical variables?

A

They are variables that divide the cases into groups, so that each case is in exactly one group (for each categorical variable)

Averages do not make sense for this type of variable.

It is also referred to as a qualitative variable.

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6
Q

What are quantitative variables?

A

They are variables that are measured or recorded by a numerical quantity.

Averages must make sense; they are also called numerical variables.

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7
Q

What is an explanatory variable?

A

The variable that explains or influences the response variable.

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8
Q

What is the response variable?

A

The variable of interest, “outcome variable”
The variable that is affected by the other.

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9
Q

What is population?

A

The population is all the individuals or objects of interest (all the possible cases). (N = population size)

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10
Q

What is a sample?

A

A sample is a subset of the population - data are collected from it (n = sample size)

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11
Q

What is a census?

A

A census is when data is gathered on the entire population.

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12
Q

Which is more highly sought after?
A sample study or a census study?

A

While census is more accurate given its thoroughness, sample size may be better because it is easy to measure and it stays static.

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13
Q

What is a parameter?

A

A parameter is a value that describes the population.

Ex. ages (8-11)

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14
Q

What is a statistic?

A

A statistic is a value that describes the sample.

Ex. The average height of the cases was 5’11

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15
Q

What is a statistical inference?

A

A statistical inference is the process of using data from a sample to learn something about the population.

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16
Q

What are two examples of inadequate sampling models?

A
  1. Volunteer Sampling
  2. Convenience Sampling
17
Q

What is sampling bias?

A

When the method of selecting a sample causes the sample to differ from the population in some relevant way.

18
Q

What element do all good sampling methods have?

A

Randomness

19
Q

What is SRS (Simple Random Sample)?

A

A method of choosing a sample in which each unit of the population has the same chance of being selected for the sample regardless of the other units chosen for the sample.

This promotes diversity and it is a better representation of the population.

20
Q

What are some other forms of bias?

A
  1. Question wording (vague or non descriptive language on one side)
  2. Context (if you could do it again would you have children example from notes)
  3. Inaccurate responses
  4. People selected chose not to participate
21
Q

What is an association?

A

Two variables are associated if values of one variable “tend” to be related to the values of another variable.

22
Q

What is causal association?

A

Two variables are causally associated if changing the value of the explanatory variable influences the value of the response variable.

23
Q

Describe whether the example implies no association, association without causation, or association with causation and name the explanatory and response variables.

Families with many cars tend to also own many TV sets.

A

Association.

  1. families with many cars - explanatory
  2. families with many TV’s - response
24
Q

Describe whether the example implies no association, association without causation, or association with causation and name the explanatory and response variables.

Taking a low-dose aspirin a day reduces the risk of MI

A

Association with Causation.

  1. taking a low-dose aspirin - explanatory
  2. Risk of MI - response
25
Q

Give an example of when association doesn’t mean causation.

A

While it is true that as the number of TV’s per 1000 people increases so does life expectancy, buying more TV’s will not help you live longer!

26
Q

What is the confounding variable?

A

The confounding variable is a third variable that is associated with both the explanatory variable and the response variable.

-can offer a explanation for an association

-if confounding variables are present, a causal association can not be determined

27
Q

What is a possible confounding variable.

Do taller people have higher IQ’s?

A

Age (adolescents)

28
Q

What is an experiment?

A

An experiment is a study in which the researcher “actively” controls one or more of the explanatory variables.

29
Q

What is an observational study?

A

An observational study is a study in which the researcher does not actively control the value of any variable, but simply observes.

30
Q

Why can observational studies never be used to establish causality?

A

Because it is very difficult to avoid confounding variables when your just observing.

31
Q

What is a randomized experiment?

A

In this type of experiment, the value of the explanatory variable for each case (unit) is determined randomly, before the response variable is measured.

32
Q

What is a treatment?

A

Treatments are the different levels of the explanatory variables.

33
Q

What is the point of a randomized experiment?

A

Because the explanatory variable is randomly assigned, it is not associated with any other variables, and therefore confounding variables are eliminated!

34
Q

Two things must be true in order to draw causality. What are they?

A
  1. The sample needs to be selected randomly - possible to generalize from the sample to population
  2. The explanatory variable must be randomly assigned - possible to make conclusions about causality
35
Q

What is a Randomized Comparative Experiment?

A

When cases are randomly assigned to different treatment groups and the results of the response variables are compared.

36
Q

What is a Matched Pairs Experiment?

A

When cases get paired up in an obvious way, or each case gets both treatments “in random order” and the individual differences in response variables are examined.

37
Q

What is Single Blind?

A

When participants are not told which treatment group they are in.

38
Q

What is Double Blind?

A

When the participants are not told, AND the people interacting with the participants and recording the results also do not know which group they are in.

Applied Probability and Statistics (3 decks)

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