Chapter 1

What is frame?

A list of all individuals within the population

Experimental unit

A person, object, or some other well defined item upon which a treatment is applied

What is a discrete variable?

A quantitative variable that either has a finite number of possible values or a countable number of possible values. CANNOT take on every possible value.

What is a continuous variable?

A quantitative variable that has an infinite number of possible values that are not countable. May take on every possible value between any two values (often rounded)

What is a convenience sample?

A sample in which individuals are easily obtained and not based on randomness (self selected: when individuals decide to participate in the study)

What is simple random sampling?

A sample size n from a population of size N is obtained through simple random sampling is every possible sample of size n has an equally likely change of occurring.

Define sample with replacement

A selected individual is placed back into the population and could be chosen a second time

What are qualitative variables?

Allows for classification of individuals based on some attribute or characteristic Ex: Gender, zip code, etc

What is lurking variable?

An explanatory variable that was not considered in a study but that affects the value of the response variable in the study. In addition, lurking variables are typically related to explanatory variables considered in the study.

Define sampling without replacement

An individual who is selected is removed from the population and can't be chosen again

If the results of the sample are not representative of the population, then the sample has a what?

Bias

What are cross-sectional studies?

Collect info about an individual at a specific point in time.

Which statistics consists of organizing and summarizing information​ collected?

Descriptive

Define Response Bias

Exists when the answers on a survey do not reflect the true feelings of the respondent. (wording of questions, interviewer error, etc)

A controlled study conducted to determine the effect varying one of more explanatory variables or factors has on a response variable. Any combo of the values of the factors is called a treatment.

Experiment

T/F: When obtaining a stratified​ sample, the number of individuals included within each stratum must be equal.

False. Within stratified​ samples, the number of individuals sampled from each stratum should be proportional to the size of the strata in the population.

Define Ratio

Has properties of the interval level and ratios of the values of the variable have meaning. Value=0 absence of quantity.

Define Ordinal

Has properties of the nominal level of measurement (specific order) Ex: Letter grades because the values of the variable can be ranked

Define Interval

Has properties of the ordinal level of measurement and the differences in the values of the variable have meaning. Ex: Temperature because differences in the value of the variable make sense. 70 degrees is 10 degrees warmer than 60 degrees. Ratio of temperature does not represent a meaningful result. 0 degree does not represent absence of heat.

What are cohort studies?

Identifies group to study (cohort). Cohort observed over long period of time. Characteristics are recorded and some people unintentionally exposed to certain factors. (cohort studies are prospective).

What is a designed experiment?

If a researcher assigns the individuals in a study to a certain group, intentionally changes the value of an explanatory variable and then records the value of the response variables for each group.

Which statistics uses methods that generalize results obtained from a sample to the population and measure the reliability of the results?

Inferential

What is an example of explanatory variable?

Level of cell phone usage

What is observational study?

Measures the value of the response variable without attempting to influence the value of either the response or explanatory variables.

What is a cluster sample?

Obtained by dividing the population into groups and selecting all individuals from within a random sample of the groups. Example: rather than collecting data from all students in an online class, each online class could be considered a cluster

What is a systematic sample?

Obtained by selecting every kth individual from the population. The first individual selected corresponds to a random number between 1 & k . Example: We decide to survery every k=8th individual. We randomly select a number between 1-8, such as 5. This means we survey the 5th, 5+8=13th, 13+8=21st, and so on.

What is a stratified sample?

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 similar in some way.

A numerical summary of a population is a what?

Parameter

What are quantitative variables?

Provides numerical measures of individuals. The values of quantitive variable can be added or subtracted and provide meaningful results. Ex: Temperature, number of days, etc.

Define nonsampling errors

Results from undercoverage, nonresponse bias, response bias, or data error

Define sampling errors

Results from using a sample to estimate info about a population. This type of error occurs because a sample gives incomplete info about a population

What is a control group

Serves as a baseline treatment that can be used to compare other treatments

A numerical summary of a sample is a what?

Statistic

What is statistics? A. Statistics is the science of​ manipulating, reorganizing, and editing information to produce the desired results. In​ addition, statistics is about providing the required answer with the desired level of confidence. B. Statistics encompasses all scientific disciplines in which random occurrences are analyzed. In​ addition, statistics references any random occurrence which is reported using percentages or proportions. C. Statistics encompasses all scientific disciplines in which percentages are​ used, data are​ analyzed, and probabilities are found. In​ addition, statistics references any mathematical model which is reported using percentages or proportions. D. Statistics is the science of​ collecting, organizing,​ summarizing, and analyzing information to draw a conclusion and answer questions. In​ addition, statistics is about providing a measure of confidence in any conclusions.

Statistics is the science of​ collecting, organizing,​ summarizing, and analyzing information to draw a conclusion and answer questions. In​ addition, statistics is about providing a measure of confidence in any conclusions.

What is random sampling?

The process of using change to select individuals from a population to be included in the sample

Define sampling bias

The technique used to obtain the samples individuals tend to favor one part of the population over another *any convenience sample and can lead to incorrect predictions*

Describe Nominal.

The values of the variables name, label, or categorize. (not in specific order) Ex: gender (categorization can't be ranked)

What are case-control studies?

These studies are retrospective, meaning, they require individuals to look back in time or requires researchers to look at existing records. In these studies individuals who have a certain characteristic may be matched with those who dont.

What are the characteristics of the individuals of the population being studied?

Variables

Define nonresponse bias

When individuals selected to be in a sample who do not respond to the survey have different opinions from those who dont

What is cofounding?

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 variables not accounted for in the study

What is an example response variable?

Whether or not brain cancer was contracted