Shared Flashcard Set

Details

Stat Test 1
Stat Test 1
33
Mathematics
02/02/2010

Term
 Statistics
Definition
 is a science that involves the extraction of information from numerical data obtained during an experiment or from a sample. It involves the design of the experiment or sampling procedure adn the collection of the data, the analysis of the data, and making inferences about the population based upon information in a sample
Term
 Population
Definition
 The entire group of individuals about which the researcher wants information   Examples: All United States Citizens All male students at VCU All sections of all courses taught this semester at VCU
Term
 Parameter
Definition
 Some characteristic of the population that the researcher wants to measure   Examples: 1.) Proportion of US citizens who voted in the 2004 presidential election 2.) Average (mean) height of all male students at VCU 3.) Proportion of all sections of all courses taught by adjunct (part-time) faculty
Term
 Greek Letters u(mu) and pi
Definition
 mean is denoted by mu proportion of successes in a population is denoted by pi
Term
 Sample
Definition
 A subset of the population that is contacted and examined to gather information   Example: when the population is all male VCU students, a sample would be all male students in this class
Term
 Statistic
Definition
 A descriptive measure, computed from data in a sample, that can be expressed or evaluated numerically.   Example: For the sample of male students in this class, one can compute the average height is a statistic
Term
 Inference
Definition
 A statement about a population based on the data collected in a sample   Example: To estimate the average height of all male VCU students we can compute the average height of the male students in this class
Term
 Distribution
Definition
 A listing of all the possible values that a characteristic can take and the number (or percentage) of times that each value occurs   Examples: 1.) Gender of student: Male____ Female____   2.) Color of car: Blue____ Red____ White____ Other____
Term
 Descriptive Statistics
Definition
 Branch of statistics concerned with numerical and graphical techniques for describing one or more characteristics of a population and for comparing characteristics among populations
Term
 Inferential Statistics
Definition
 Branch of statistics in which we use data and statistics computed from a sample to make inferences (statements) about a population   The information used to make these inferences is often some type of descriptive statistic
Term
 Replication/Repetition
Definition
 Statistics involve experiments or samples in which either repeated measurements are made on a single subject or measurements are made on many different subjects. This is referred to as replication (or replication).
Term
 Constant
Definition
 A characteristic whose measurements do not change in repeated trials over time   Example: 1.) Number of days in january each year (always 31) 2.) Number of minutes in an hour (always 60)
Term
 Variable
Definition
 A characteristic whose measurements vary(or change) from trial to trial or individual to individual   Examples: 1.) Heights of students 2.) Grades on a test
Term
 Qualitative or Categorical Variable
Definition
 A variable whose measurements vary in kind or name, but not in degree. This implies that one level of a categorical variable cannot be considered to be greater than or better than another level   Example: 1.) Gender: male or female 2.) Eye color 3.) Social security number
Term
 Quantitative Variable
Definition
 A variable whose measurements vary in magnitude from trial to trial, meaning some order or ranking can be applied to the levels   Examples: 1.) Number of students in a particular class 2.) Weight of a typical student 3.) Grades on a test
Term
 Discrete Quantitative Variable
Definition
 A quantitative varible whose measurements can assumer only a countable number of possible values   Example: 1.) Number of students in a particular class 2.) Number of cars in a parking deck 3.) Grades on a test
Term
 Continuous Quantitative Variable
Definition
 A quantitative variable whose measurements can assume any one of a countless number of values in a line interval. It is usually a measurable quantity or something that is calculated, such as rates, averages, proportions, and percentages   Examples: 1.) Weight of a typical student 2.) Percentage of students who pass a course
Term
 Sampling Procedure
Definition
 we select a sample of a population and only measure(or contact) the subjects in the sample
Term
 Representative Sample
Definition
 The sample should be as representative of the population as possible, meaning that the characteristics of the sample should mimic the characteristics of the population.
Term
 Bias
Definition
 Bias exists when some subjects or individuals are systematically favored over others. A sample which is representative of the population should be free of bias. If the sample is not representative, then the results will be biased in favor of the responses of those which are over-represented
Term
 Selection Bias
Definition
 Selection bias occurs when one or more types of subjects are systematically excluded from the sample.   When selection bias exists, the results from the sample can only be inferred to part of the population. the inference cannot be made to the entire population, but only a subset of the population. This is referred to as undercoverage
Term
 Nonresponse Bias
Definition
 When an individual randomly chosen to be a part of a sample cannot be contacted or fails (or refuses) to respond, then we have a nonresponse bias. This is often a big problem in surveys or polls, in which the person either throws the survey away or refuses to answer the questions of those conducting the poll.
Term
 Response Bias
Definition
 when respondents give inaccurate information or if the interviewer influences the subject to respond in a certain way due to the way the questions are phrased, this is response bias. This is especially a concern with legal or social behavior issues.
Term
 Haphazard or volunteer response sample
Definition
 A haphazard sample involves selecting a sample by some convient mechanism that does not involve randomization.   A mall survey in which questionnaires are distributed to people as they walk through the mall, or a campus survey in which students are questioned as they walk across campus are two examples of haphazard samples.
Term
 A volunteer response sample
Definition
 A volunteer response sample exists when subjects volunteer to be part of the study. Examples include telephone call-in polls, internet surveys, newspaper survey, call in talk show surveys, etc.   The problem with volunteer response samples is that often those who choose to respond often have strong opinions, most often negative opinions, and hence volunteer response samples over-represent those with strong opinions.
Term
 Bias
Definition
 haphazard and volunteer response samples are particularly prone to bias, particularly nonresponse bias
Term
 random samples
Definition
 samples in which the subjects are chosen randomly to be in the sample are often representative of the population and are, for the most part, free of bias   When each subject of the population has a positive and equal probability of being selected for the sample, then we are using a probability sampling design to select our sample. this will reduce(or eliminate) bias.
Term
 Simple Random Sampling
Definition
 with simple random sampling we make a list of all possible individuals in the population and randomly choose n of the subjects in such a way that every set of n subjects has an equal chance of being selected for the sample. This procedure is impartial, meaning the interviewer has no discretion as to whom is to be included in the sample
Term
 Simple Random Sampling
Definition
 1. Label the individuals in the population from 1 to N. 2. Use a table of random digits, like on page 315, to randomly select a sample of n numbers between 1 and N. These numbers correspond to the individuals who are selected to be in the sample.
Term
 Stratified Random Sampling
Definition
 The population is naturally divided into two or more groups of similar subjects, called strate   Example: Strata 1= males Strata 2 = females   Simple random samples are then selected from each stratum, and combined to give the complete stratified random sample
Term
 Stratified Random Sampling
Definition
 The number chosen from each stratum should correspond to the percentage of the total population in each stratum, with at least one individual chosen from each stratum
Supporting users have an ad free experience!