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A condition applied to the experimental unit. |
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The group in a designed experiment that receives the treatment of interest (The variable being manipulated). (In designed experiments, this group is that which receives the real treatment to be judged, not the placebo.) |
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The group in a designed experiment that receives a placebo, and serves as a benchmark against the experimental group. |
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A controlled study in which one or more treatments are applied to experimental units. The experimenter then observes the effect of varying these treatments on a response variable. Control, manipulation, randomization, and replication are the key ingredients of a well-designed experiment. |
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Completely randomized design |
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An experiment in which the experimental units are randomly assigned the treatment. |
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A quantitative variable that has an infinite number of possible values that are not countable. |
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Double-blind is a type of designed experiment in which neither the experimental unit nor the experimenter knows what treatment is being administered to the experimental unit. |
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The characteristics of the individuals within the population. |
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A fact or proposition used to draw a conclusion or make a decision. |
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Qualitative or Categorical variables allow for classification of individuals based on some attribute or characteristic. |
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Observations corresponding to a qualitative variable. |
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Observations corresponding to a quantitative variable. |
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Quantitative variables provide numerical measures of individuals. Arithmetic operations such as addition and subtraction can be performed on the values of a quantitative variable and provide meaningful results. |
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Information being conveyed is based on casual observation, not scientific research. |
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A list of all individuals in a population along with certain characteristics of each individual. |
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An observational study measures the characteristics of a population by studying individuals in a sample, but does not attempt to manipulate or influence the variable(s) of interest. Observational studies are sometimes referred to as ex post facto (after-the-fact) studies because the value of the variable of interest has already been established. |
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Control (Dealing with Factors) |
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Control is fixing the factors at one predetermined value throughout the experiment. These are variables whose effect on the response variable is not of interest. |
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Explanatory Variables, or factors, are the variables manipulated to determine the effect on the response variable in a designed experiment. |
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Replication (In a Designed Experiment) |
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Replication is applying a treatment to more than 1 experimental unit. |
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A way to look at and organize a problem so it can be solved. (A means of attack) |
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A way of approaching a problem to attempt to solve it. |
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1. Identify the research objective 2. Collect the information needed to answer the questions posed in (1). 3. Organize and summarize the information. (This step is referred to as descriptive statistics.) 4. Draw conclusions from the information. |
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Statistics that consists of organizing and summarizing the information (data) collected. |
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Statistics that uses methods to take results obtained from a sample, extends them to the population, and measures the reliability of the result. |
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A lurking variable is a variable that is related to either the response or predictor variable, or both, but is excluded from the analysis. (Hidden variables, or variables that have failed to be accounted for.) |
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A matched-pairs design is an experimental design in which the experimental units are paired up. The pairs are matched up so that they are somehow related (example: same person before and after a treatment, twins, husband and wife, same geographical location, lawyer and cesspool cleaner, and so on.) There are only two levels of treatment in a matched-pairs design. Sometimes called before-after or pretest-posttest experiments. v1: A randomized block design in which the experimental units are somehow related. |
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The probability of a link between 2 variables in a observational study. Indicates a relationship, but not necessarily a cause and effect. |
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The probabilty in a designed experimet that the explanatory variable causes the resulting response variable value. (Cause and Effect) |
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A list of all the individuals within the population. |
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A sample obtained by simple random sampling. |
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The number that in a random-number generator that provides an initial point for the generator to start creating random numbers. (The seed can be any nonzero number.) |
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Sampling without replacement |
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Creating a sample from a frame without allowing any individual to be selected twice. |
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Sampling that is done by separating the population into nonoverlapping groups called strata and then obtaining a simple random sample from each stratum. |
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A single group in stratified sampling. (Plural is Strata) |
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Nonoverlapping groups obtained by breaking up a population by some common value or trait. (Stratum is the singular) |
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A systematic sample is obtained by selecting every kth individual from the population. The first individual selected is a random number between 1 and k. |
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A person, object, or some other well-defined item that is a member of the population being studied and upon which a treatment is applied. (See Experimental unit and Individual.) |
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A stratified sample is obtained by separating the population into nonoverlapping groups called strata and then obtaining a simple random sample from each stratum. The individuals within each strata should be homogeneous (or similar) in some way. |
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Sampling that is done by selecting every kth individual from the population. The first individual selected corresponds to a random number between 1 and k. *f(x) = p + (x-1)k Where p = randInt(1,k) and k = Int(N/n)* |
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Sampling done by selecting all individuals within a randomly selected collection or group of individuals. |
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A cluster sample is a sample obtained by selecting all individuals within a randomly selected collection or group of individuals. |
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Sampling in such a way the individuals are easily obtained. |
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A sample in which the individuals are easily obtained. |
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Error that results from using sampling to estimate information regarding a population. This type of error occurs because a sample gives incomplete information about the population. (Expected error). |
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The individuals themselves decide to participate in a survey. Also known as voluntary response samples. |
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Voluntary response samples |
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Samples in which the individuals decide to participate. Also known as self-selected. |
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Errors that result from the survey process. They are due to the nonresponse of individuals selected to be in the survey, to inaccurate responses, to poorly worded questions, to bias in the selection of individuals to be in the survey, and so on. |
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When a statistic consistently overestimates or underestimates a parameter. |
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Underrepresented is a insufficiently or inadequately represented subset of the population, that as a result of the sampling method tends to get excluded. |
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Qualitative or Categorical variables allow for classification of individuals based on some attribute or characteristic. |
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One in which the respondent must choose from a list of predetermined responses. |
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The explicit statement of the problem. The statement should provide the experimenter with direction. In addition, the statement must identify the response variable and the population to be studied. |
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One in which the respondent is free to choose his or her response. |
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Nonresponse is when a individual selected for the sample does not respond to the survey. |
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A method to help minimize nonresponse. Involves contacting the individual again, possibly with a different method. (See leave-me-alone-already) |
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A method to help minimize nonresponse. Involves Bribery, or indications that their opinion will be valued in making some decision. (See waiting on hold hearing "Your call is important to us".) |
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The variable in a designed experiment that represents the variable of interest. |
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The science of collecting, organizing, summarizing, and analyzing information in order to draw conclusions. |
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The population is the group that is to be studied. |
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A subset of the population. |
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A person, object, or some other well-defined item that is a member of the population being studied, and upon which a treatment is applied. |
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Descriptive statistics consists of organizing and summarizing the information collected. |
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Inferential statistics uses methods that generalize results obtained from a sample to the population and measure their reliability. |
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An inactive substance against which investigational treatments are compared for efficacy. example: An innocuous medication such as a sugar tablet. |
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A person, object, or some other well-defined item to which a treatment is applied. |
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