Terms  Definitions 

υ 
Population mean

strata 
group of similar individuals

Bias 
systematic favoring of an outcome

Factors 
The explanatory variables in an experiment.

sample 
a representative subset of a population, examined in hope of learning about the population

stratified 
sampling design in which the population is divided into several strata, and random samples are then drawn from each stratum

experiment 
treatment is imposed on experimental units

1 Histogram 
used adjacent bars to show distribution of quantitative variable

Stratified Sampling 
Dividing a population into subgroups (strata) and then taking a separate random sample from each stratum.

outliers 
extreme values that don't appear to belong with the rest of the data

systematic sample 
a sample drawn by selecting individuals systematically from a sampling frame

population parameter 
mathematical measures taken from the entire population like the population mean and standard deviation

cluster 
sampling design in which entire groups are chosen at random

disjoint sets 
sets which contain no common elements

quantitative variable 
takes numerical values for which arithmetic operations such as adding and averaging make sense

Center 
A value that divides the observations so that about half take larger values and about half have smaller values.

2 Median 
middle value. Usually used when data is skewed

Measurement Bias 
A form of inaccurate measurement in which the data consistently overestimate or underestimate the true value of an event.

standardized value 
value found by subtracting the mean and dividing by the standard deviation

matched design 
when our data values are not independent of one another and are related somehow to one subject  it is a form of blocking

outcome 
an individual result of a component of a simulation

categorical variable 
one of two variable types; determines which of several CATEGORIES an individual belongs to; qualitative; adjectives; anything that falls into a CATEGORY; displayed with bar charts & pie graphs (ex. red, blonde, brunette hair color) (ex. letter grades on a test)

Dotplot 
A picture of numerical data in which each observation is represented by a dot on or above a horizontal measurement scale

Voluntary Response Sample 
A voluntary response sample consists of people who choose themselves by responding to a general appeal.

3 Census 
A sample that consists of the entire population

data table 
an arrangement of data in which each row represents a case and each column represents a variable

single blind 
when either the subjects or the people who have contact with them do not know which treatment a subject has received

Intersection 
The event "A and B" consists of all experimental outcomes that are in both the events A and B

SD( XY) (only when x and y are independent) 
√(Var(X)+Var(Y))

Association Doesn't Imply Causation 
An association between an explanatory variable x and a response variable y, even if it is very strong, is not by itself good evidence that changes in x actually cause changes in y.

disjoint or mutually exclusive 
two events that have no common outcomes

ladder of powers 
places in order the effects that many reexpressions have on the data

density curve 
a curve with an area of exactly 1 (100%) beneath it; alawys on or above the horizontal axis; median divides area under curve in half; mean is the 'balance point'; when mean and median are the same, curve is symmetric

Choosing an SRS 
Choose an SRS in two steps:
Step 1: Label. Assign a numerical label to every individual in the population. Step 2: Table. Use Table B to select labels at random. 
4 Statistically Significant 
When the p value falls below the alpha level

Strength of a relationship 
Determined by how close the points in the scatterplot lie to a simple form such as a line.

Normal Model (sampling distribution model) 
If we draw repeated random samples of the same size, n, from some population and measure the proportion we get for each sample, then the collection of these proportions will pile up around the underlying population proportion, p, in such a way that a historgram of the sample proportions can be modeled by ______.

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