Determine whether the underlined numerical value is a parameter or a statistic.
The average annual salary of 50 of a company's 800 employees is $54,000
Statistic, because the data set of salaries of 50 employees is a sample
Determine whether the variable is qualitative or quantitative.
Amount of disk space in gigabyte
The variable is quantitative because it is a numerical measure.
Determine whether the quantitive variable is discrete or continuous.
Goals scored in a season by a soccer player
The variable is discrete because it is countable
The Gallup Organization contact 1178 adults who are 20 to 90 years of age and lived in Europe and ask whether or not they had voted in the last federal election.
What is the population of the study?
What is the sample in the study?
Population: Adults who are 20 to 90 and lived in Europe
Sample: The 1178 adults who are 20 to 90 and live in Europe
Setup Size (in) Screen Type Channels
A 50 Projector 299
B 52 Plasma 120
C 54 Plasma 423
D 47 Projector 270
E 41 Projector 290
What are the individuals being studied?
What are the variables and their corresponding data being studied?
Size is a?
Screen type
Individuals: The set ups A through E of widescreen high- definition televisions.
Variables: Size, screen type, channels.
Size: Continuous variable
Screen Type: Qualitative variable
Number of channels: Discrete variable
What is meant by confounding?
Confounding in a study occurs when the effects of two or more explanatory variables are not separated. Therefore, any relations that may exist between an explanatory variable and the response variable may be due to some other variable or variable not acco
Cross- Sectional Study?
Observation studies that collect information about individuals at a specific point in time or over a very short period of time.
For example: a researcher might want to asses the risk associated with smoking by looking at a group of people, determining how
What does it mean when an observation study is retrospective?
Requires the individuals to look back in time or require the researcher to look at existing record.
What does it mean when an observational study is prospective?
A prospective study collects the data over time.
Population
The entire group to be studied
Sample
A subset (smaller set) of the population to be studied
Individual
A person or object that is a member of the population being studied
Statistic
A numerical summary of a sample
Parameter
A numerical summary of a population
Descriptive Statistics
Organizing and summarizing data using numbers, tables and graphs
Inferential Statistics
Methods that take a result from a sample, extend to the population and measure the reliability of the result
Qualitative Variable (categorical cariable)
Allow for classification of individuals based on some attribute or characteristic; averaging these values would not make sense. (EX: hair color, favorite color, location)
Variables
Characteristics of the individuals within the population (EX: height, weight, hair color)
Discrete
a quantitative variable that has either a finite number of possible values or a "countable" number of values, usually answers the question "how many people, objects, etc
Continuous
A quantitive variable that has an infinite number of possible values that are NOT countable. These are usually measurements, such as "how much weight, height, speed, volume, etc
Observational Studies
No attempt was made to influence the individuals in the study
Measures the value of the response variable without attempting to influence the value of either the response or explanatory variable
Designed Experiements
Each group was intentionally exposed to various levels of radiation
A researcher assigns the individuals to a certain group, intentionally changes the value of an explanatory variable, and then measures the response variable
Explanatory Variable ("x")
The value(s) of the manipulated characteristic(s)
We think of this as the "input
Response Variable ("y")
The value being measured as a result
We think of this as the "output
Lurking Cariable
An explanatory variable that was not considered in a study but that affects the value of the response variable in the study
Census
is a list of all individuals in a population along with certain characteristics of each individual
How reliable is a census?
Not very reliable, very impossible/ inaccurate
Frame
Numerate a list of the population- each individual needs a unique number
Stratified Random Sample
Separate the population into strata (groups based on a common characteristic EX: size, career, age
Systematic Sample
Selecting every "k" individual from population to create the sample
EX: A manager might survey every 10th customer in his/ her store
Cluster Sample
Randomly selecting a location (zipcode, classroom, building, floor department) or time (between 12M- 1PM) and surveying every individual int hat location or time frame
Convenience Sample
Self Selected (Response cards on table)
Voluntary response
Pop- up surveys on websites
Multi- Stage Sample
Large scale surveys- any combination of the different ways to sample
Sampling Bias
Convenience sampling, under coverage (not everyone in the population has an equal chance of being selected)
Non- Response Bias
Voluntary surveys
Can be reduced by using callback and incentives
Response Bias
Survey not conducted correctly
Interviewer Error
Interviewer influenced answers (if a cop asks you if you were speeding)
Misrepresented Answers
Inflated/ Deflated results (if you ask a woman her weight)
Wording/ Order Of The Questions
Do you agree with killing innocent beings?
Salesman
Factor
Explanatory variables could be one or more per experiment
Treatment
What is going to be done to the individuals in the experiment
Unit
Individuals participating in the experiment (person, object, animals)
Control Group
Baseline treatment, uses a placebo with appropriate
Blinding
A technique used so that the subject does not know which treatment they are receiving (single blind), generally only necessary for human subjects
Double Blind
Neither the subject nor the administrator know which treatment is being received; generally necessary when a product is trying to be sold/ purchased
What does it mean when sampling is done without replacement?
Once an individual is selected, the individual cannot be selected again
Qualitative
Statistics consists of organizing and summarizing information collected
Inferential
Statistic uses methods that generalize results obtained from a sample to the population and measure the reliability of the results
STATISTIC OR PARAMETER?
A sample of employees is selected and it is found that 55% own a computer
Statistic because the value is a numerical measurement describing a characteristic of a sample
Cross- Sectional Study
Observational studies that collect information about individuals at a specific point in time or over a very short period of time
Case Control Study
Observational studies that are retrospective, meaning that they require individuals to look back in time or require the researcher to look at existing records
Confounding
Occurs when the effects of two or more explanatory variables are not separated. Therefore, any relation that may exist between an explanatory variable and the response variable may be due to some other variable or variable not accounted for in the study
Individual
Person or object that is a member of the population being studied