Stat - Exam #1 Flashcards Preview

Spring 2015 > Stat - Exam #1 > Flashcards

Flashcards in Stat - Exam #1 Deck (134)
Loading flashcards...

What is Statistics?

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


What kind of data is used in Statistics?

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


What are the techniques of gathering statistical data?

1. Sampling;
2. Descriptive Stats;
3. Inferential Stats


What is Sampling?

-Techniques used to collect info
— Major technique = Simple Random Sampling;
— COLLECTING techniques


What are Descriptive Statistics?

-Techniques used to condense and describe sets of data;
— Major techniques = Frequency Tables, histograms, and summary numbers;


What are Inferential Statistics?

-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


What are Statistical Methods?

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


What is a Population?

-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


What is a Sample?

A SUBSET of the population;
— Larger the sample size the better, but the METHOD is more important than the size


What is an Individual?

ONE object from the POPULATION


What is the goal of Sampling?

To collect…
1. a measurable numbers of individuals that...
2. represent the population
*Measuring the sample gives info about the population


What are the 4 sampling techniques?

1. **Simple random = best;
2. Stratified;
3. Systematic;
4. Cluster


How can sampling be done?

1. WITH replacement;
2. WITHOUT replacement


What are the non sampling errors?

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


What is Simple Random Sampling?

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


What does Random sampling do?

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


What is the method of Random Sampling?

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)


What are the 3 classes of data?

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


What are the types of data?

1. Qualitative;
2. Quantitative = Discrete or Continuous


What is Qualitative Data?

Data that can be calcified by some mutually exclusive and exhaustive quality of individuals;
EX: Color, religion, gender


What is Quantitative Data?

Data that are numericanl and allow the use of arithmetic


What is Discrete Data?

-Easily countable number of possible values;
EX: 1-10 ( number of items)


What is Continuous Data?

- Infinite number of possible values;
EX: Time, weight, length


What is the method to identify TYPES OF DATA?

1. Pick any TWO data points;
2. Can they be ordered?
3. Countable number of values between?
—NO = Continous;
—YES = Discrete


What is a Census?

-Study that measures a characteristic of EVERY individual in a population;
— Observational;
— DOES NOT involve a sample;
— Measure the whole population
EX: US Census


What is an Observational Study?

-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


What is Experimental Design?

-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


What is Independent Design?

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


What is Dependent Design?

-One half of the experimental units are chosen randomly and the second half are chosen by matching characteristics;
-“Matched-Pairs Design"


When do you use an Experimental Design?

When you can BOTH:
1. Control the individuals characteristics and
2. Control the treatment
*If you CAN’T do both, use observational