Flashcards in Stat - Exam #1 Deck (134)

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1

## What is Statistics?

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-The science of COLLECTING, ORGANIZING and SUMMARIZING and ANALYZING information to draw conclusions;

-Science of data

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## What kind of data is used in Statistics?

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Probabilistic data = data that characteristics of being unknown for one observation, but many observations is know;

— characterize well in the long run, but unknown individually

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## What are the techniques of gathering statistical data?

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1. Sampling;

2. Descriptive Stats;

3. Inferential Stats

4

## What is Sampling?

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-Techniques used to collect info

— Major technique = Simple Random Sampling;

— COLLECTING techniques

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## What are Descriptive Statistics?

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-Techniques used to condense and describe sets of data;

— Major techniques = Frequency Tables, histograms, and summary numbers;

— ORGANIZING and SUMMARIZING techniques

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## What are Inferential Statistics?

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-Techniques used to systematically draw conclusions about a population from a set of sample data;

-Gather population information from a sample;

— Interpretation of data by generalizing info from a sample to apply to a population

— Major tools = Hypothesis testing and confidence intervals;

— ANALYZING techniques

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## What are Statistical Methods?

### -Combo of descriptive and inferential techniques (collect, organize, summarize, analyze)

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## What is a Population?

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-The totality of element in a well-defined group to be studied;

-MUST be WELL-DEFINED by clearly stating what exact and specific elements (people, animals, etc) DO and DO NOT belong in the population

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## What is a Sample?

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A SUBSET of the population;

— Larger the sample size the better, but the METHOD is more important than the size

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## What is an Individual?

### ONE object from the POPULATION

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## What is the goal of Sampling?

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To collect…

1. a measurable numbers of individuals that...

2. represent the population

*Measuring the sample gives info about the population

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## What are the 4 sampling techniques?

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1. **Simple random = best;

2. Stratified;

3. Systematic;

4. Cluster

13

## How can sampling be done?

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1. WITH replacement;

2. WITHOUT replacement

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## What are the non sampling errors?

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1. Coverage errors = incomplete population;

2. Nonresponse erros = cannot measure selected element;

3. Inaccurate response errors = poor records, lying;

4. Measurement erros = ambiguous questions, crude tools

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## What is Simple Random Sampling?

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A method of choosing a sample such that each sample of the same size has the same change of being chosen;

- Each individual has equal chance of being chosen

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## What does Random sampling do?

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1. DOES remove SELECTION bias from the sample;

2. Does NOT affect the natural variability of data;

3. Does NOT guarantee a representative sample;

**ONLY way to allow inferences (informed guesses) about the population

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## What is the method of Random Sampling?

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1. Assign every individual in a population a number;

2. Select individuals to be in the sample by:

— Random number table or

— Random number generator

(Data > Random Variates > Distribution)

18

## What are the 3 classes of data?

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1. Constant = measurement gives only one possible value;

2. Variable = repeated measure yields many possible values;

3. Random Variable = randomly varying values (value determined by chance:

**Stats is concerned with data from random variables

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## What are the types of data?

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1. Qualitative;

2. Quantitative = Discrete or Continuous

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## What is Qualitative Data?

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Data that can be calcified by some mutually exclusive and exhaustive quality of individuals;

EX: Color, religion, gender

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## What is Quantitative Data?

### Data that are numericanl and allow the use of arithmetic

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## What is Discrete Data?

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*Quantitative;

-Easily countable number of possible values;

EX: 1-10 ( number of items)

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## What is Continuous Data?

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*Quantitative;

- Infinite number of possible values;

EX: Time, weight, length

24

## What is the method to identify TYPES OF DATA?

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1. Pick any TWO data points;

2. Can they be ordered?

—NO = QUALITATIVE:

—YES…

3. Countable number of values between?

—NO = Continous;

—YES = Discrete

25

## What is a Census?

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-Study that measures a characteristic of EVERY individual in a population;

— Observational;

— DOES NOT involve a sample;

— Measure the whole population

EX: US Census

26

## What is an Observational Study?

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-Study that measures a characteristics in a sample WITHOUT controlling the units or treatment;

— Called an “Ex Post Study” (after the fact) because values have already been established;

— Determines ASSOCIATION, not cause;

EX: students heights in a class

27

## What is Experimental Design?

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-Study that measure a characteristic in a sample WITH CONTROLLING units or treatment;

EX: measure wt. gain of 3 emails on a week long high protein diet

1. Independent or

2. Dependent

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## What is Independent Design?

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*Experimental;

-Where all experimental units are randomly chosen and assigned to treatments randomly

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## What is Dependent Design?

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*Experimental;

-One half of the experimental units are chosen randomly and the second half are chosen by matching characteristics;

-“Matched-Pairs Design"

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