CHAPTER 1 Definitions
Statistics
a collection of procedures and principles for gathering data and analyzing info to help people make decisions when faced
with uncertainty.
Standard deviation
roughly, the average difference between individual data and the mean.
Rate
at which something occurs, the # of times it occurs per # of opportunities for it to occur
Risk
of a bad outcome in the future est. by using the past rate 4 outcome assuming the future is like the past.
Base risk/baseline risk:
rate or risk at a beginning time period of under specific conditions.
Population:
collection of all individuals about which info is desired
Random sample
subset of the pop selected so that every ind has a specified prob of being part of sample
Sample survey
investigators gather opinions or other info form each ind included in sample
Margin of error
+ or – 1/ sq. root of n.
interval that is 95% certain to contain the truth about the population ex.
# of individuals in
sample were to be
increased
, the margin of error would
decrease
Observational study
participants are merely observed and measured
Variable
characteristic that differs from one individual to next, numerical or categorical
Confounding variable
variable not main concern of study but may be partially responsible 4 observed results
Randomized experiment
a study which treatments are randomly assigned to participants
Treatment
specified regimen or procedure assigned to participants by experimenter
Placebo
a pill or treatment designed to look like active treatment but have no active ingredients.
Statistically significant
relationship or difference is one that is large enough to be UNLIKELY to have occurred in the sample if
there was NO RELATIONSHIP in the population.
CHAPTER 2
Q1:
25% of the values are at or below this or 75% are at or above this value
Median:
50% of the values are at or below this value or 50% are at or above this value
Q3:
75% of the values are at or below this value or 25% are at or above this value
right skewed:
hump to left of the graph & other data “tailing” to the right. Mean: greater than the median
Resistance:
median & IQR: less resistant to extreme observations than the mean, standard deviation, range
Emperical Rule
About
__ of the data will be in the interval mean ± ___
(68%, s)
(95%, 2 x s)
(99%, 3 x s)
Outlier Identifier
Greater than Q3 + 1.5 × IQR, or
Smaller then Q1  1.5 × IQR
Statistic
summary measure computed from sample data,
parameter
is a summary measure for an entire population
Quantitive
measurement variable, numerical variable, continuous variable
Explanatory
variable thought to partially explain the
response
variable
One or Two Categorical variable: tally, cross tabulation, chi square
Pie charts
single categorical variable
bar graphs
one or two categorical variables (2 mainly)
dot plot/five number summary
quantitive value
QUANTITIVE
Distribution:
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 Spring '08
 BARROSO,JOAOR
 Statistics, Regression Analysis, Standard Deviation, Statistical terminology, statistically significant relationship, Confounding variable variable

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