The Process of Statistics
A statistic is:
A numerical summary of a sample
What is a variable?
A characteristic of an individual within the population. (They VARY! If not, they would be constants instead.)
If you count to get to the value of a quantitative variable, it is ________. If you measure to get the value of a quantitative variable, it is __________.
1. discrete
2. continuous
A(n) __________ ___________ measures the value of the response variable without attempting the influence the value of either the response or explanatory variables.
observational study
How is a stratified sample obtained?
You separate the population into groups called strata and then obtain a simple random sample from each stratum. (The individuals within each stratum should be similar in some way!)
The entire group to be studied is called the __________. An __________ is a person or object that is a member of the population being studied. A ______ is a subset of the population that is being studied.
population
individual
sample
Qualitative or categorial variables allow for classification of individuals based on:
some attribute or characteristic.
Data is:
the list of observed values for a variable.
A(n) __________ __________ is a study in which a researcher assigns individuals to a certain group, intentionally changing the value of an explanatory variable, and then records the value of the response variable for each group.
designed experiment
How is a systematic sample obtained?
(So if every k = 8th individual, we pick a number between 1 and 8. If we choose 5, then we start with 5, then add 8 (=13), add 8 again (=21), etc.)
What type of statistics uses methods that result from a sample, extend it to the population, and measure the reliability of the result?
Inferential statistics
____________ variables provide numerical measures of individuals. The values of a __________ variable can be added or subtracted and provide meaningful results.
quantitative (QUANTITY = how many?)
Give an example of a topic in terms of variables and data.
Gender is a variable; the observations male and female are data.
What element of a study can occur when the effects of two or more explanatory variables are not separated?
Confounding
How is a cluster sample obtained?
You select all individuals within a randomly selected collection or group of individuals. (Imagine a mall parking lot! Each subsection of the lot could be a cluster. 🚗 )
A numerical summary of a population is a:
parameter
This type of variable is quantitative and has either a finite number of possible values or a countable number of possible values.
Discrete variables! (A discrete variable cannot take on every possible value between any two possible values.)
What are the four levels of variable measurement? What does each one mean for the variable it describes?
nominal level = the values of the variable name, label, or categorize
ordinal level = properties of nominal level PLUS naming scheme allows for the variable to be arranged in rank order
interval level = properties of ordinal level PLUS differences in the variable values have meaning. Addition and subtraction can be performed on values of an interval level variable! A value of zero does NOT = the absence of the quantity.
ratio level = properties of interval level PLUS ratios of the value of the variable have meaning. Multiplication and division can be performed on values of a ratio level variable! A value of zero DOES = the absence of the quantity.
What is the difference between a confounding variable and a lurking variable?
While both variables occur when the effects of two or more variables cannot be distinguished from one another, a confounding variable has been considered in a study, and a lurking variable has not been considered.
What is a convenience sample? What is the most popular form of convenience sampling?
A sample in which the individuals are easily obtained and not based on randomness.
Self-selected/voluntary response samples = the individuals decide to participate on their own
List the four steps involved in determining the process of statistics.
1. Identify the research objective.
2. Collect the data needed to answer said questions.
3. Describe the data.
4. Perform inference.
A __________ variable is a quantitative variable that has an infinite number of possible values that are not countable. A __________ variable may take on every possible value between any two values.
continuous (goes on to INFINITY!)
What do sampling errors result from? What about nonsampling errors?
Sampling errors result from using a sample to estimate information about a population (and the sample gives incomplete info).
Nonsampling errors result from undercoverage, nonresponse bias, response bias, or data-entry error.
Name the three types of observational studies and their distinctive features.
Cross-sectional studies: collect info about individuals at a specific point in time or over a very short period of time.
Case-control studies: retrospective (requiring individuals to look back in time/require researcher needs to look at existing records.
Cohort studies: A group of individuals (the cohort) is observed over a long period of time.
What are the three sources of bias in sampling?
1. Sampling bias (the technique used to obtain responses tends to favor one population over another)
2. Nonresponse bias (individuals selected to participate who do not respond hold different opinions from those who do respond)
3. Response bias (answers on a survey do not reflect the true feelings of the respondent)