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# Prob and Stat c.1/14

### ch.1,14.1,14.2, margin of error

TermDefinition
variable a characteristic or attribute that can assume different values
data the values of the variables assume
random variable variables whose values are determined by chance
data value (datum) each value of the data set
probability chance of an event occurring
population consists of all subjects
sample consists of only a select few of a population
3 examples of how statistics is used in everyday life fields of human endeavor, analyze the results of a survey, used as a tool in scientific research to make decisions based on controlled experiments
3 reasons to study statistics become better consumers, in your professional field, to conduct research
descriptive consists of the collection, organization, summarization, and presentation of data
inferential consists of generalizing from samples to populations, performing estimations and hypothesis tests, determining relationships among variables, and making predictions
qualitative variables that can be placed into distinct categories (not numbers)
quantitative numerical and can be ordered or ranked
discrete variables that assume values that can be counted
continuous variables that can assume an infinite number of values between and two specific values. (often fraction and decimals)
boundaries length-15cm-14.5-15.5cm
nominal gender, zip code, political party
interval SAT scores
ratio height, weight, area
two purposes for data collection describe situations or events, help people make better decisions before acting
3 ways to collect data surveys, mailed questionnaire, personal interview
telephone surveys advantage-lest costly, people are truthful disadvantages-not all people are surveyed
random sampling generating numbers by computer
systematic sampling every kth subject
stratified sampling dividing population into groups then selection a couple from each group
cluster sampling diving into groups then using everyone in that group
statistics The science of conducting studies to collect, organize, summarize, analyze, and draw conclusions
observational study age of motorcycles
experimental study types of instruction affects the number of sit-ups done
advantages for observational occurs in a natural setting can be done in dangerous or unethical situations
advantages of experimental studies researchers can decide how to select and group subjects researchers can control or manipulate individual variables
disadvantages of observational a definite cause and effect situation cannot be determined since other factors have an effect on the results can be expensive and time consuming
disadvantages of experimental may occur in unnatural settings Hawthorne Effect- subject knows that they are participating and will act differently
Independent variable explanatory variable- the one that is being manipulated EX. type of instruction
Dependent Variable outcome variable-resultant variable-the variable that is being studied to see if it changes due to manipulation EX. number of sit-ups
quasi-experimental when random assignments are not possible-use an intact group
confounding variable one that influences the results of the dependent variable but cannot be separated from the independent variable
biased sample selected incorrectly an error was made in the selection
unbiased sample chosen at random from a population. Representative of the whole population
sequential sampling used in quality control successive units taken from the production line and sampled to ensure the product meets the standards
double sampling a large population is given a questionnaire to see who meets the requirements for the study. After reviewing the questionnaire a smaller population is defined and a sample is chosen from this population
margin of error 1/square root of n population
interval p +/- 1/ square root of n populaiton
Created by: hstonestreet15