Chapter 2 - Measures of Location and Spread Flashcards
what are the measures of location
minimums
maximums
quartiles
percentiles
deciles
means
modes
medians
what are the measures of spread
range
interquartile range
standard deviation
variance
what is the variance in terms of standard deviation
the square of the standard deviation
how can you find the mean from an ungrouped frequency table
for each row, multiply x by f, then divide by the sum of f
how can you find the mean from a grouped frequency table
find the midpoint of x, then multiply it by f, and divide by the sum of f
why is the mean from grouped frequency tables an estimate
because we dont know the true distribution of the values within each group
how can you fin the position of the median
on listed data: add up the f column. add one, then divide by 2
on grouped data: add up the f column, divide by 2, dont round, then use linear interpolation
what measures can we use interpolation to find
quartiles
deciles
percentiles
what must we do before linear interpolation
make the classes overlap if they dont already
we do we favour the IQR over the range
the IQR is less likely to be influenced by outliers and anomalies
what is variance and standard deviation
variance: a measure of spread which can be defined as the average squared distance from the mean
standard deviation: roughly the average distance from the mean
what does msmsm mean
the mean of the squares minus the mean
variance = (the sum of (original values^2)/frquency) - mean^2
how will a measure of spread increase if we add 10 to each value
it will not change
how will a measure of location increase if we add 10 to each value
it will increase by 10
how will a measure of spread increase if we multiply each value by 3
it will triple
