Chapter 1 Flashcards
The science of collecting, organizing, summarizing, and analyzing information to draw conclusions or answer questions
Additionally, about providing a measure of confidence in any conclusions
Statistics ***
Statitiscs is about providing a measure of ____________ in any conclusion.
Confidence
The information, fact or proposition used to draw a conclusion or make a decision
Describes characteristics of an individual
Data
I key aspect of data is that they…
Vary
Ex:different height, hair color
One goal of statistics is to…
Describe and understand sources of variability*
The entire group of individuals to be studied
Population
An __________ is a person or object that is a member of the population being studied
Individual
Subset of the
Population that is being studied
Sample
Consist of organizing and summarizing data. Describe data through numerical summaries, tables, and graphs.
Descriptive statistics
A ____________ is a numerical summary based on a SAMPLE*
A ___________ is a numerical summary of a POPULATION*
Statistic ex:grades
Parameter***
Uses methods that can take results from a sample, extend them to the population, and measures the reliability of the result
Inferential statistics
The process of statistics. What are the four steps?
- Identify the research objective
- Collect the data needed to answer the question(s) posed in (1)
- Describe the data
- Perform inference
Allow for classification of individuals based on some attribute or characteristic
Qualitative or categorical variables
Provide numerical measures of individuals. The values can be added or subtracted and provide meaningful results
Quantitative variables
What are the two quantitative variables?
Discrete variable- whole numbers, ex:people
Continuous variable, has an infinite number of possible values. Ex: weight
The list of observations a variable assumes is called ______.
Well gender is a ________, The observations, male or female, are ______.
Data
Variable, data
A variable is at the __________ level of measurement if the values of the variable name, label, or categorize. In addition, the naming scheme DOES NOT allow for the values of the variables to be arranged in a ranked, or specific, order.
Nominal level of measurement
Ex: M&M colors
A variable is at the ___________ level of measurement if it has the properties of the nominal level of measurement and the naming scheme allows for the values of the variables to be arranged in a rate, or specific, order.
Ordinal level of measurement
Ex: class in school, freshman/senior
A variable is at the _________ level of measurement if it has the properties of the ordinal level of measurement in the difference in the values of the variable have meaning. A value of zero in the measurement does not mean the absence of the quantity.
Arithmetic operations such as addition and subtraction can be performed on values of the variable.
Interval
A variable is at the _______ level of measurement if it has the properties of the interval level of measurement in the ratios of the values of the variable have meaning. The value of zero in the level of measurement means the absence of the quantity. Arithmetic operations such as multiplication and division can be performed on the values of the variable.
Ratio level of measurement
Sometimes the explanatory variable is referred to as the…
Predictor variable
In the cell phone usage/cancer risk study,
whether or not brain cancer was contracted is the _________ variable
The level a cell phone usage is the ________ variable.
Response
Explanatory
In research, we wish to determine how varying the amount of an ____________ Variable affects the value of a __________ variable.
Explanatory, response
an __________ Study measures the value of the response variable without attempting to influence the value of either the response or explanatory variables.
Researchers observe the behavior of the individuals in the study without trying to influence the outcome of the study.
Observational study
If a researcher assigns the individuals in a study to a certain group, intentionally changes the value of the explanatory variable, and then records the value of the response variable for each group, the researcher is conducting a __________ experiment.
Designed
_____________ in a study 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 very well may be due to some other variable or variables not accounted for in the study.
Confounding
A ___________ variable is an explanatory variable that was not considered in a study, but that affects the value of the response variable in the study. In addition, these variables are typically related to any explanatory variables considered in the study
Lurking
Ex: in the flu shot example… health, age, mobility etc.
Observational studies do not allow a researcher to claim ___________, only _________.
Causation
Association***
What kind of experiment must be done if a researcher wants to identify cause-and-effect relationships among variables in the study?
A design experiment*****
Need to know
A ______________ variable is an explanatory variable that was considered in a study whose effect cannot be distinguished from a second explanatory variable in the study.
Confounding
What are the three types of observational studies?
- Cross-sectional studies
- Case-control study’s
- Cohort studies
Observational studies that collect information about individuals at a specific point in time, or over a very short period of time.
- usually inexpensive
- relatively quick to complete
Cross-sectional studies
These observational studies are retrospective, they require individuals to look back in time or require the researcher to look at existing records. individuals who have certain characteristics are matched with those that do not.
- researchers want individuals to be homogeneous (so that it does not affect the response variable being studied)
- disadvantages are that individuals may have trouble remembering or may not be truthful
- advantages are that the studies are also relatively inexpensive and quick to carry-out
Case-control studies
This study first identify a group of individuals to participate in the study. They are then observed over a long period of time. Over this time period, characteristics about the individual are recorded. Because the data is collected over time the studies are prospective.
- involves many individuals over long periods of time
- if individuals drop out due to the long timeframe, study results can be misleading
- even so, they are considered the most powerful type of observational study
Cohort studies
Is a list of all the individuals in a population along with certain characteristics of each individual
Census
____________ or ______________ must determine which individuals are part of the sample, rather than convenience!
Chance or randomness
What are the four sampling techniques?
- simple random sampling
- stratified sampling
- systematic sampling
- cluster sampling
Sampling technique of using chance to select individuals from a population to be included in the sample.
Random sampling
If convenience is used to obtain a sample, the results of the survey are….
Meaningless***
In simple random sampling…
n =
N =
n = sample (little n, small sample) N= population (big N for large population)
A sample size of n from a population size N is obtained through ______________ if every possible sample of size n has an equally likely chance of occurring.
Simple random sampling
A ___________ sample is obtained by separating the population into non-overlapping groups called strata and then obtaining a simple random sample from each Stratum . The individuals within each Stratum should be homogeneous or similar in someway.
Stratified
A ____________ sample is obtained by selecting every Kth individual from the population. The first individual selected is a random number between one and k.
Systematic
A ____________ sample is obtained by selecting ALL Individuals within a randomly selected collection or group of individuals.
Cluster
A __________ sample is one in which the individuals in the sample are easily obtained.
Any studies that use this type of sampling generally have results that are suspect* results should be looked upon with extreme skepticism.
Convenience
Most large scale surveys obtain samples using a combination of techniques known as ___________ sampling
Multistage
What are three bias in sampling?
- Sampling bias-sample tends to favor one part of the population over another.
Can result in UNDERCOVERAGE - Non-response bias- those who do not respond to the survey have different opinions from those who do respond. This can be improved by rewards and incentives
- Response bias- when answers on a survey do not reflect the true feelings of the respondent
Types of errors in sampling….
- Data entry error
- non-sampling errors: ??
- sampling error: The sample gives incomplete information about the population
