Statistics
study of the collection analysis, interpretation, presentation, and organization of data
population
set of people or subjects whose properties are to be described and analyzed by the data collector.
frequency polygon
data representation with graph/dots by which the lines must be drawn to touch the horizontal axis
group frequency
64, 56,67,89,90,09,90,76
stem and leaf plot
the stem consists of the tens digit digits and the leaf is the second part
the mean- notation /x
(average) sum of the data items divided by the number of items- Ex(sum of data)/na (number of items)
Medium
1. arrange the numbers in order from smallest to largest
2. if the amount is odd, then the middle number is the medium
3. if the number is even, take the medium of the two middle numbers
The mode
data item that occurs the most often. If you have a mode in a first set you will have the frequency in the other.
the midrange
smallest data items and largest data items. If everything increases by 5 it stays the same
standard deviation- formula; second measure of dispursion that is dependent on all the data item
deviation from each data item mean of data set... the square root of the (data item- the mean) squared / n-1
sample
a subset or subgroup of the population
random sample
(subset of the population) sample obtained in such a way that every element in the population has an equal chance of being selected for the sample
grouped frequency distribution
data that is tallyed into an appropriate range class
class width
the span/difference between all the of consecutive lower class limits of data in grouped frequency distributions
calculating the mean for frequency distribution
Ex(f)/n
medium position
to find the position of the medium.... n+1/2. If you get a split number position, such as 9.5, you know the medium will be the mean of position 9 and 10
midrange
found by adding the lowest and highest data values and dividing the sum by 2
range- first measure of dispertion
quick but rough measure of dispersion, it is the difference between the highest and lowest data value in a data set
standard deviation rule 68-96-99.7
68-95-99.7 rule
1. approximetly 68% of the data items fall within one standard deviation of the mean in both directions
2. 95 of the data items fall within 2 standard deviations of the mean in both directions
3. 99.7 of the data items fall within 3 standa
z - scores
describes how many standard deviations a dtat item in a normal distribution lies above or below the mean. the x score can be obtained using
*z-score= data item- mean/standard deviation
*data item=(z score)(standard deviation) + mean
*Data items above the
what are the 4 measures of central tendency
the mean/medium/mode/midrange
normal distribution
Histogram/bellcurve: when sample size increases so does the graphs symmetry, and if it were possible to measure the entire population.
what is the sum of deviations from the mean for a data set
always o