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41 Cards in this Set

  • Front
  • Back
Data
Collections of observations, such as measurements, genders, or survey responses
Statistics
The science of planning studies and experiments, obtaining data, and then organizing, summarizing, presenting, analyzing, interpreting, and drawing conclusions based on the data.
Population
The complete collection of all measurements of data that are being considered.
Census
Collection of data from every member of a population.
Sample
Sub-collection of members selected from a population.
Sampling Method:
Voluntary response (or self-selected)
samples often have bias (those with special interest are more likely to participate).
Statistical significance
is achieved in a study when we get a result that is very unlikely to occur by chance.
Practical significance
Common sense might suggest that the finding does not make enough of a difference to justify its use of its use or to be practical.
Potential Pitfalls
Misleading conclusions
Too small of a sample used
Loaded questions were used
The order of the questions
Nonresponse
Missing Data
Precise Numbers
Percentages
Parameter
a numerical measurement describing some characteristic of a population.

Population = Parameter
Statistic
a numerical measurement describing some characteristic of a sample

Sample = Statsistic
Quantitative Data
(or numerical data)
Consists of numbers representing counts or measurements.

Ex: Weights, Ages
Categorical Data
(or qualitative data)
Consists of names or labels (representing categories)

Ex: gender, Shirt numbers on professional athletes uniforms
Quantitative Data

Discrete Data
results when the number of possible values is either a finite number or a 'countable' number

Ex: 0, 1, 2, 3, ...
The number of eggs that a hen lays
Quantitative Data

Continuous (numerical) Data
results from infinitely many possible values that correspond to some continuous scale that covers a range of values without gaps, interruptions, or jumps.

Ex: The amount of milk that a cow produces; e.g. 2.343115 gallons per day.
Nominal Level
characterized by data that consist of names, labels, or categories only, and the data cannot be arranged in an ordering scheme (such as low to high).

Ex: Survey responses yes, no, undecided.
Ordinal Level
involves data that can be arranged in some order, but differences between data values either cannot be determined or are meaningless.

Ex: Course grades A, B, C etc.
Interval Level
involves data that can be arranged in order and the difference between any two data values is meaningful. However, there is no natural zero starting point (where none of the quantity is present).

Ex: Years 1000. 2000, 1776 etc.
Ratio Level
the interval level with the additional property that there is also a natural zero starting point (where zero indicates that none of the quantity is present); for values at the level, differences and ratios are meaningful.

Ex: Prices of college textbooks ($0 represents no cost, a $100 book costs twice as much as a $50 book)
Observational study
observing and measuring specific characteristics without attempting to modify the subjects being studied.
Experiment
apply some treatment and then observe its effects on the subjects.
Simple Random Sample
a sample of n subjects is selected in such a way that every possible sample of the same size n has the same chance of being chosen.
Random Sample
members from the population are selected in such a way that each individual member in the population has an equal chance of being selected.
Systematic Sampling
select some starting point and then select every kth element in the population.
Convenience Sampling
Using results that are easy to get.
Stratified Sampling
Subdivide the population into at least two different subgroups that share the same characteristics, then draw a sample from each subgroup.
Cluster Sampling
Divide the population area into sections (or clusters). Then randomly select some of those clusters. Now choose all members from selected clusters.
Multistage Sampling
Collect data by using some combination of the basic sampling methods.

In a multistage sample design, pollsters select a sample in different stages, and each stage might use different methods of sampling.
Cross-sectional study
Data are observed, measured, and collected at one point in time.
Retrospective (or case control) study
Data are collected from the past by going back in time.

Ex: examine records, interviews
Prospective (or longitudinal or cohort) study
Data are collected in the future from groups sharing common factors (called cohorts).
Randomization
is used when subjects are assigned to different groups through a process of random selection. The logic is to use chance as a way to create two groups that are similar.
Replication
is the repetition of an experiment on more than one subject.
Blinding
is a technique in which the subject doesn't know whether he or she is receiving a treatment or a placebo.
Double-Blind
1) The subject doesn't know whether he or she is receiving the treatment or a placebo.

2) The experimenter does not know whether he or she is administering the treatment or placebo.
Confounding
occurs in an experiment when the experimenter is not able to distinguish between the effects of different factors.
Randomized Block Design
a block is a group of subjects that are similar, but blocks differ in ways that might affect the outcome of the experiment.
Matched Pairs Design
compare exactly two treatment groups using subjects matched in pairs that are somehow related or have similar characteristics.
Rigorously Controlled Design
carefully assign subjects to different treatment groups, so that those given each treatment are similar in ways that are important to the experiment.
Sampling error
the difference between a sample and the true population result, such an error results from chance sample fluctuations.
Non-sampling error
sample data incorrectly collected, recorded, or analyzed (such as by selecting a biased sample, using a defective instrument, or copying the data incorrectly.