Terms  Definitions 

Parameter 
A population measure

stratified sampling 
slice of population

randomization 
random assignment of experimental units to treatments or of treatments to trials, the best defense against bias.

standard deviation and IQR 
Measures of spread.

Frequency 
Number of times each outcome occured

Histogram 
Used adjacent bars to show distribution of quantitative variable

principals of experimental design 
control, randomize, replicate

Statistics 
a characteristic or measure obtained by using the data values from a sample

Scatterplot 
plots explanatory vs. response for bivariate data of quantitative variables only!! We can add a categorical component by changing symbols or colors...

Nonresponse 
Individual chosen for the sample can not be contacted or does not cooperate

Y intercept 
the value of y when x=0

cluster sampling 
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

Bias 
Any systematic failure of a sampling method to represent its population

sampling frame 
the individuals or clusters of individuals who might actually be selected for inclusion in the sample

Symmetric 
If a histrogram of a certain distribution has both the right and left sides approximately equal.

multistage sampling 
sampling schemes that combine several different sampling methods at different stages

percentile 
The value that a specified percent of the observations fall below.

Undercoverage 
Some groups in the population are left out of the process of choosing the sample.

the correlation always falls between these two numbers 
1 and +1

Bernoulli Trials 
Have 2 outcomes, probability of a success is constant, trials are independent

statistical inference 1 
provide an alternative method for producing data in such circumstances

quantitative graphs 
histograms, dot plots, stem and leaf plots, box plots

outlier 
a point that lies outside the overall pattern of the data

uniform distribution 
a distribution whose shape is evenly distributed throughout the values it takes

The Three Principles of Experimental Design 
Conrtol, Randomization, Replication

Placebo effect 
Patients' response may be because of a dummy treatment. Many patients respond favorably to any treatment. Due to trust to doctor and expectation of a cure.

trimmed mean 
a measure of center in which the observations are first ordered from smallest to largest, then one or more observations are deleted from each end, and finally the remaining observations are averaged; in terms of sensitivity to outliers, the trimmed mean is a composite between the mean and the median

Systematic Sample 
A sample drawn by taking every n^th person

Outcome variable 
a variable which is studied in order to see if it has change significantly due to the manipulation of the explanatory variable

Lurking 
A variable is lurking if it drives two other variables

Chebyshev's Rule 
for any number k >_ 1, at least 100(11/k squared)% of the observations in any data set are within k standard deviations of the mean; the percentage value is typically conservative in that the actual percentages often considerably exceed the stated lower bound

least squares regression line 
The leastsquares regression line of y on x is the line that makes the sum of the squares of the vertical distances of the data points from the line as small as possible.

sample space 
a list of all possible outcomes of a random variable

Simple Random Sample (SRS) 
A simple random sample of size n consits of n individual units or individuals chosen in such a way that all possible sets of size n have an equal chance of being chosen.

law of Large Numbers 
in the long run, the results of the repeated trials of a random event will appraoch the theoretical probability that we expect for the event

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