Statistical Methods STT 200
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This 4 page Class Notes was uploaded by Aryanna Jerde on Saturday September 19, 2015. The Class Notes belongs to STT 200 at Michigan State University taught by Staff in Fall. Since its upload, it has received 44 views. For similar materials see /class/207818/stt-200-michigan-state-university in Statistics and Probability at Michigan State University.
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Date Created: 09/19/15
Chapter 12 Sample surveys Population the entire group of individuals or instances Parameter numerical characteristic of a population u population mean deviation 0 population standard deviation p correlation 9 proportion Distribution model density Vocabulary Sample a subset of a population Statistic a number computed from data 97 sample mean s sample standard deviation r sample correlation A P sample proportion Distribution histogram dotplot Sampling Frame a list of individuals from which a sample is selected Sampling Variability each random sample is different Sampling Design a method of taking a sample Sample Size the number of elements in a sample If a goal is to estimate population parameters or distribution a sample should represent the whole population and hence 1the sample individuals should be selected at random so that 2 each set of the same size has the same chance of being selected A sample drawn in this way is called a simple random sample SRS Sampling Designs 0 SRS each set of size n has the same chance to be selected Stratified Random Sample a sampling design in which the population is divided into groups strata and random samples are then drawn from each mwm Cluster Sample a sampling design in which first groups or cluster are chosen and then samples are drawn within them Multistage Sample design that combines the above methods Systematic Sample there is pattern in selecting a sample but the starting point is random Bias a systematic failure of a sample to represent a population Sources of bias Voluntary Response Sample large group is invited to response but only those who responded count Notrepresentative 0 Convenience Sample include in a sample individuals which are at hand Notrepresentative notrandom o Undercoverage some portion ofa population is not sampled o Nonresponse bias when large fraction of sampled individuals fail to response 0 Response bias wrong wording order etc of questions that suggest certain response Chapter 13 Experiments OBSERVATIONAL STUDY a study based on observed data with no manipulation of factors employed for example a survey Usually used to estimate population parameters 0 Retrospective data consists of past outcomes 0 Prospective data will consist of future outcomes EXPERIMENTS a study based on manipulation of factors treatments employed and analysis of observed responses Usually used to determine causal relationship A researcher must identify at least one explanatory variable called factor and its values levels to be assigned Any combination of different factors and their levels is called a treatment A researcher observes responses to different treatment Principles of Experimental Design 1 Control Control sources of variation other than coming from different treatments For example blinding either subjects or those who evaluate responses or both 0 singleblinding o doubleblinding Placebo fake treatment N Block Block or match subjects to reduce variability of responses to the same treatment
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