module 2 - measures of location and spread Flashcards
what is the formula for calculating the mean?
sum of the data values / the number of data values
how do you calculate the mean in a frequency table?
the sum of all the products of the data
values and their frequencies/
the sum of the frequencies
how do you find the upper and lower quartile of discrete data?
lower= divide N by 4
upper = find 3/4 of N
when do we use interpolation and what is the formula?
when the data is presented in a grouped frequency table
value- LB (CF) = position - LB (CW)
/ UB(CF) - LB(CF) / UB(CW) - LB(CW)
where
UB = upper bound
LB = lower bound
CF= cumulative frequency
CW= class width
VALUE= what value on the CF table the solution is
POSITION= the percentile we are looking for
what is the variance and what is the equation for it?
variation = how much the values deviate from the mean
(Σx²)/ n – (Σx/n)² = the mean of the squares, minus the square of
the mean
Σ represents “sigma” meaning sum of all
how do you find out standard deviation from the variance
square root the variance
how do you get standard deviation values on a calculator
shift - setup
3- statistics
frequency? : on
setup - 3 statistics
insert X and Y values
OPTN,
3 - gives values
what is the equation for variance
the mean of the squares minus the square of the mean
(Σx²)/ n – (Σx/n)²
why do we use coding in data values
simplifies statistical calculations
coded set of data values are easier to work with
(you will be given an equation to code the data)
if the data is coded using the formula
y= (x-a) / b
how is the mean of the coded data given
and how is the standard deviation given
mean = x bar - a /b (where xbar is the mean of the uncoded data)
standard deviation sigma (y) = sigma (x) /b
where sigma (x) is standard deviation of original data
how do you code class intervals
code the midpoint of the class interval
