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51 Cards in this Set
- Front
- Back
Data
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are observations (such as measurements, genders, survey responses) that have been collected
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Statistics
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Is a collection of methods for planning studies and experiments, obtaining data, and then organizing, summarizing, presenting, analyzing, interpreting, and drawing conclusions based on the data.
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Population
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Is the complete collection of all elements (scores, people, measurements, and so on) to be studied. The collection is complete in the sense that it includes all subjects to be studied
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Cenus
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Is the collection of data from ever member of the population
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Sample
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is a sub collection of members selected from a population
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Parameter
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Is a numerical measurement describing some characteristic of a population
In New York City, there are 3250 walk buttons that pedestrians can press at traffic intersections. It was found that 77% of those buttons do not work (based on data from the article "For Exercise in New York Futility, Push Button" by Michael Luo, New York Times). The firgure of 77% is a parameter because it is based on the entire population of all 3250 pedestrian push buttons |
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Statistics
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Based on a sample of 877 surveyed executives, it is found that 45% of them would not hire someone with a typographic error on their job application. That figure 45% statistic because it is based on a sample, not the entire population of all executives.
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Quantitative data
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Consist of numbers representing counts or measurements
The weights of supermodels |
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Qualitative data
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Can be seperated into different categories that are distinguished by some nonnumeric characteristic
The genders of professional athletes |
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Discrete data
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Results when the number of possible values is either a finite number or a "countable" number. (That is, the number of possible values is 0 or 1 or 2 and so on.)
The number of eggs that hens lay are discrete data because they represent counts |
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Continuous data
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Results from infinitely many possible values that correspond to some continuous scale that covers a range of values without gaps, interuptions, or jumps.
The amounts of milk from cows are continuous data because they are measurements that can assume any value over a continuous span |
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Nominal Level of Measurement
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Characterized by data that consist of names, labels, or categories only. The data cannot be arranged in an ordering scheme (such as low to high).
Yes/no/undecided: survery responses of yes, no and undecided Colors: The colors of cars driven by college students (red, black, blue, white, magenta, mauve, and so on) |
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Ordinal Level of Measurement
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They can be arranged in some order, but differences between data values either cannot be determined or are meaningless
Course Grades: A college professor assigns grades of A, B, C, D, F Ranks: Magazine ranks cities according to their "livability" Those ranks (first, second, third, and so on) determine an ordering. |
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Interval Level of Measurement
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Like the ordinal level, with the additional property that the difference between any two data balues is meaningful. However,data at this level do not have a natural zero starting point (where none of the quantity is present)
Temperatures: There are no natural startying point. The value deg F might seem like a starting point, but it is arbitrary Years: Time does not begin in the year zero, so the year zero is arbitrary instead of being a natural zero starting point representing "no time" |
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Ratio Level of Measurement
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Is the interval Level with the addition property that there is also a natural zero starting point (where zero indicates that none of the quantity is present). For values at this level, differences and ratios are both meaningful
Weights: Weights (in carats) of diamond engagement rings Prices: prices of college textvooks (0$ does represent no cost, and a 90$ book is three times as costly as a $30 book). |
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Voluntary Response Sample/ Self-reflected Sample
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Is one in which the respondents themselves decide whether to be included
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Small Samples
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Conclusions should not be based on samples that are far too small
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Graphs
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Graphs-such as bar grapghs and pie charts can be used to exaggerate or understate the true nature of data
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Pictographs
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Drawing of objects, called pictographs, may also be misleading. SOme objects commonly used to depict data inclue three-dimensional objects. When drawing such objects, artist can create false impressions that distort diffwerences.
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Percentages
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Misleading or unclear percentages are sometimes used. If you take 100% of some quantity, you are taking it all. ( It shouldnt require 110% effort to make sense of the preceding statement)
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Loaded Questions
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There are many iussues affecting survey questions. Survey Questions can be loaded or intentionally worded to elicit a desired response
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Order of Questions
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Sometimes survey questions are unintentionally loaded by such factor as the order of the items being considered.
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Nonresponse.
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A nonresponse occurs when someone either refuses to respond to a survey question, or the person is unavailable.
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Missing data
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Results can sometimes be dramatically affected by missing data
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Correlation and Causality
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Correlkation does not implu causality
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Self-Intrest Study
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Studies are sometimes sponsored by parties with intresent to promote
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Precise Numbers
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Because a figure is very precise, many people incorrectly assume that it is also accurate
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Deliberate Distortions
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False advertising based on a survey
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Observational Study
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We pbserve and measure specific characteristics, but we don't attempt to modify the subjects being studied
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Experiment
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We apply some treatement and then process to observe its effect on the subjects ( subjects in experiments are called experimental units)
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Cross-sectional study
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Data are observed, measured, and collected at one point in time
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Retrospective (case-control) study
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Data are collected from the past by going back in time (through examination of records, interviews, and so on).
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Prospective (longitudinal/cohort) study
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Data are collected in the future from groups sharing common factos
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Confounding
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Occurs in an experiment when you are not able to difstinguish among the effects of different factors
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Placebo effect
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Occurs when an untreated subjects reports an improvement in sumptoms
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Blinding
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a technique in which the subject doesn't know whether he or she is receiving a treatement or a placebo
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Double blind
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Means the blinding occured at 2 levels
(1) The children being injected didn't know whether they were getting the treatement or placebo (2) the doctors who gave the injections and evaluated the results did not know either |
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Block
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Is a group of subjects that are similar
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Completely Randomized Experimental Design
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Subjects are assigned to different treatment groups through a process of random selection
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Rigorously Controlled Design
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In which subjects are very carefully chosen so that those given each treatment are similar in the ways that are important to the experiment
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Replication
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Repetition of an experiment on sufficiently large groups of subjects is called replication, and replication is used effectiveluy when we have enough subjects to recognize difference from different treatment
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Random Sample
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Members from the population are selected in such a way that each individual member has an equal chance of being selected
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Simple random sample
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of n subjects is selected in such a way that ever possible sample of the same size n has the same chance of being chosen
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Probability sample
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involves selecting members from a population in suh a way that each member has a known (but not necessarily the same) chance of being selected
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Systematic Sampling
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We select some starting point and then select every kth element in the population
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Convenience sampling
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We simply use results that are very easy to get
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Stratified Sample
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We subdividing the population into at least 2 different subgroups so that subjects within the same subgroup share the same characteristics then we draw a sample from each subgroup
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Cluster sampling
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we first divide the population area into sections then randomly select some of those clusters and then choose all the members from those selected clusters
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Multistage sample
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involves the selection of a sample in different stages that might use different methods of sampling
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Sampling Error
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Is the difference between a sample result and the true population result; such an error results from chance sample fluctuations
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Nonsampling Error
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Occurs when the sample data are incorrectly collected, recorded, or analyzed
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