1.1 Intro to the Practice of Statistics
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.
What is Statistics?
Explain the difference between an observational study and a designed experiment.
What is an observational study does not attempt to influence the value of the response or explanatory variables. A designed experiment, a researcher intentionally changes the value of the explanatory variable and records the value of the response variable for different groups.
Explain why simple random sampling is preferred.
What is it maximizes the likelihood that the individuals chosen for the sample are representative of the whole population?
Separates the population into nonoverlapping groups and then obtains a simple random sample from each. Individuals in each group should be similar in some way.
What is stratified sampling?
Errors that result from sampling bias, response bias, or data-entry error. Such errors could also be present in a complete census of the population.
A person or object that is a member of the population being studied.
What is an Individual?
Observational study or experiment? A study in which balding men were compared with non-balding men at one point in time found that balding men were 70% more likely to have heart disease.
What is an observational experiment?
If used, the results of the survey are meaningless.
What is convenience sampling?
Obtained by selecting every k’th individual from the population. The first individual selected is a random number between 1 and k, p.
What is a systematic sample?
Name the three sources of bias
What is sampling, nonresponse and response.
Parameter or statistic? The average score for a class of 28 students taking a calculus midterm exam was 72%.
What is a Parameter?
Definition for review; a numerical summary of a population.
Not a statistic because our population is the class and all 28 students took the test. It would be a statistic if we said 72% of students passed.
A survey is conducted asking 400 people, “Do you prefer Coke or Pepsi?” Observational Study or Designed Experiment?
What is an observational study
In simple random sampling, all outcomes have a _______ probability of occuring.
What is equal?
To determine customer opinion of its boarding policy, Southwest Airlines randomly selects 60 flights during a certain week and surveys all passengers of the flights.
What is a cluster sample?
What is sampling bias? Uses just the southwest corner (sample) to estimate the entire village (population). It is entirely possible that the southwest corner could be the rich area or vice versa.
Define each variable as qualitative or quantitative. Number of siblings, number on a jersey, and a student id number.
What is quantitative, qualitative, qualitative?
Students are randomly divided into two groups. One group is taught using traditional techniques; the other is taught using a reformed method. After 1 year, each group is given an achievement test to compare proficiency. Name the response and explanatory variables in the study.
What is the technique taught (explanatory variable) and the achievement test score (response variable)?
The process of using chance to select individuals from a population to be included in the sample.
What is Simple Random Sampling?
Explain the difference between a cluster sample and a stratified sample.
What is stratified sampling uses simple random sampling after dividing the population into groups, cluster sampling takes the entire group after dividing.
To determine public opinion of the police department, the police chief obtains a cluster sample of 15 census tracts within his jurisdiction and samples all households in the randomly selected tracts. Uniformed police officers go door to door to conduct the survey.
Explain the different between a discrete and continuous variable.
What is a discrete variable is a quant variable with a fixed number of possible values (can be counted). A continuous variable is a quant variant with an infinite number of possible values.
Explain the difference between a cohort study, a cross-sectional study and a Case-control study.
What is a cohort follows a group of individuals over a long period of time, cross-sectional collects information about individuals at a specific point in time or over a short period of time, and case-control studies are retrospective.
The reason we care about sampling types.
What is so we can understand potential bias?
To estimate the percentage of defects in a recent manufacturing batch, a quality-control manager at Intel selects every 8th chip that comes off the assembly line starting with the 3rd until she obtains a sample of 140 chips.
What is systematic sampling?
The results of the sample are not representative of the population?