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41 Cards in this Set
- Front
- Back
Descriptive Statistics
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Numerical, graphical and tabular methods for organizing and summarizing data
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Population
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Entire collection of individuals or measurements about which information is desired
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Sample
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A part of the population selected for study
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Categorical data
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Individual observations are categorical responses (nonnumerical)
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Numerical data
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Individual observations are numerical (quantitative) in nature
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Discrete numerical data
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Possible vaus are isolated points along the number line
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Continuous numerical data
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Possible values form an entire interval along the number line
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Bivariate / Multivariate data
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Observations consist of two (bivariate) or more (multivariate) responses or values
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Frequency distribution for categorical data
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Table that displays frequencies (or relative frequencies) for each of the possible values of a categorical variable
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Bar chart
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A graph of a frequency distribution for a categorical data set; each category represented by a bar, and area of the bar is proportional to the corresponding frequency or relative frequency
When to use: categorical data What to look for: frequently and infrequently occurring categories |
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Dotplot
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A picture of numerical data in which each observation is represented by a dot on or above a horizontal measurement scale
When to use: small numerical data sets What to look for: -Representative/typical values in the data set -Extent to which the data values spread out -Nature of the distribution of values along the number line -Presence of unusual values in the data set |
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Data Analysis Process
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1. Understand nature of the problem
2. Decide what to measure and how to measure it 3. Data collection 4. Data summarization and preliminary analysis 5. Formal data analysis 6. Interpretation of results |
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Inferential statistics
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Branch of statistics that involves generalizing from a sample to the population from which it was selected and assessing the reliability of such generalizations
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Relative Frequency
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Fraction or proportion of the observations resulting in the category
Relative freq = frequency/ number of observations in the data set |
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Observational study
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A study that observes characteristics of one or more existing populations; goal is to draw conclusions about corresponding population or show differences between 2+ populations
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Experiment
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A procedure for investigating the effect of experimental conditions (which are manipulated by the experimenter) on a response variable
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Simple random sample
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A sample selected in a way that gives every different sample of size n an equal change of being selected
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Stratified sampling
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Dividing a population into subgroups (strata) and then taking a separate random sample from each stratum
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Cluster sampling
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Dividing a population into subgroups (clusters) and forming a sample by randomly selecting clusters and including all individuals or objects in the selected clusters in the sample
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1 in k systematic sampling
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Sample selected from an ordered arrangement of a population by choosing a starting point at random from the first k individuals on the list and then selecting every kth individual thereafter
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Confounding variable
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A variable that is related both to group membership and to the response variable
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Measure or response bias
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The tendency for samples to differ from the population because the method of observation tends to produce values that differ from the true value
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Selection bias
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The tendency for samples to differ from the population because of systematic exclusion of some part of the population
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Nonresponse bias
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The tendency for samples to differ from the population because measurements are not obtained from all individuals elected for inclusion in the sample
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Treatments
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The experimental conditions imposed by the experimenter
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Extraneous factor
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Variable that is not of interest in the current study by is thought to affect the response variable
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Direct control
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Holding extraneous factors constant so that their effects are not confounded with those of the experimental conditions
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Blocking
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Using extraneous factors to create experimental groups that are similar with respect to those factor, thereby filtering out their effect
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Randomization
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Random assignment of experimental units to treatments or of treatments to trials
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Replication
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A strategy for ensuring that there is an adequate number of observations on each experimental treatment
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Placebo effect
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A treatment that resembles the other treatments in an experiment, but that has no active ingredients
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Control group
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A group that receives no treatment or one that receives a placebo treatment, used to compare to experimental group
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Single-blind experiment
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An experiment in which the subjects don't know which treatment they received but the individuals measuring the response do know which treatment was received, or an experiment vice versa
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Double-blind experiment
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An experiment in which neither the subjects nor the individuals who measure the response know which treatment was received
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Census
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A study that obtains information from an entire population
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Sampling w/o Replacement
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Once an individual from the population is selected for inclusion in the sample, it may not be selected again in the sampling process
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Sampling w/ Replacement
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After an individual from the population is selected for inclusion in the sample and the corresponding data are recorded, the individual is placed back in the population and can be selected again in the sampling process
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Convenience Sampling
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Using an easily available or convenient group to form a sample
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Voluntary Response Sampling
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Samples rely entirely on individuals who volunteer to be a part of the sample; extremely unlikely that individuals participating are representative of any larger population of interest
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Design
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The overall plan for conducting an experiment
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What are the 4 key concepts in designing an experiment?
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1) Randomization
2) Blocking 3) Direct Control 4) Replication |