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18 Cards in this Set

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  • Back
what is statistics?
a science of data
what is data?
numbers with a context
what are individuals?
the objects described by a set of data
what is a variable?
any characteristic of an individual
wjat os a categorical variable?
takes numerical values for arithmetic operations such as adding averageraging make sense. The values of quantative variables are usually recorded in a unot of a measurement such seconds or kilograms
what is exploratory data analysis?
uses graphs and numerical summaries to describe the variables in a data set and the relations among them,.
How do we explore data?
begin by exmaining each varibale itself. begin with graphs
what is the distribution of a veriable?
tells us how often it takes these values of a categorical varable are labels of categories
How do you find a mean?
add the values of all the observations and divide by the number of observations
what is a median?
the midpoint of a distribution
how do you find medians?
(1) arrange all observations in order of size, from smallest to largest
(2) if the number of observations is oddd, the median M is the center observation in the ordered list. Find the location of the meidan by counting (n+1)/2 observations up from the bottom of the list.
(3) if the number of the observation is even, the median M is the mean of the two center obserations in the ordered list. The location of the median is agains (n+1)/2 from the bottom of the list
how do you calculate quartarlies?
(1) locate the medium
(2) Q1 is to the left of the median
(3) Q3 is to the right
How do you calculate the IQR?
IQR= Q3-Q1
How do you find standard deviation?
(X1-MEAN)+(X2-MEAN)+(X3-MEAN)
OVER
N-1

TAKE SOLUTION

DIVIDE BY N

SQUARE ROOT THAT ANWSER
Approximately 68% of all observation lie between ______ of _________.
the standard deviation

the mean
approx. 95% of observations fall between _____ of the ______.
2(standard deviation)

of the

mean
approx. 99.7 of observations fall between ________ of the _______.
3(standard deviation) of the mean
If x is an observation from a distribution that has mean and standard deviation, the standardized value of x (often called the z-score) is what?
z= x-mean
over
standard deviation