stats chapter 3

requirements for constructing classes

-classes shouldnt overlap -classes should not have any gaps between them -the classes should have the same width

how to compute a frequency polygon

-compute the class midpoints (add upper class limit to lower class limit/ 2) -plot the frequency of each class above each class mid point -connect the points -tie down each end by subtracting/ adding the class width to the midpoints

good practices for constructing pie charts

-each category should be labeled with the category name and its nice to include the relative frequency -pie charts are not as effective when there are too many categories or if several relative frequencies are very small (think too many skinny slices)

what are the physical requirements for a histogram

-remove the spaces between consecutive bars -use numerical classes

rules for stem and leaf plots

-stem consists of all the digits except for the right most digit and the leaf consists of the right most digit -you need a key -you can break down stems 1-4, then 5-9 provides shape of data

good practices in constructing bar graphs

-the categories should be spaced equally under apart and the rectangles should have the same widths -the scale where the bars start should begin with 0 and should be incremented in reasonable steps which go somewhat, but not significantly, beyond the largest frequency or relative frequency -dont chop the bars

cautions

-unclear scale -truncated scale -innaccurate displays ---lengths of bars in bar charts do not match their frequencies ---slices of pie in pie charts that are not proportional to their relative frequnecies -misleading or distracting graphics

pie chart

-used to display relative frequency distributions

why would you use a frequency polygon over a histogram

-you can compare the slopes -same slope = no change

pareto chart

a bar graph where the bars are arranged in descending order

dot plot

a graph where a dot is placed over the observation each time it is observed using a number line

frequency distribution

a table that organizes a dataset with the data values in the left column and the respective frequencies in the right column

what is the class width

difference between consecutive lower (or upper) class limits

stem and leaf plot

displays the same visual patterns as histograms but contain more information than histograms because you dont categorize your data

relative frequency formula

frequency/sample size

what are histograms good for

identifying the shape of a distribution

class width equation

largest value - smallest value/ number of classes

how to determine the angles for each category in a pie chart

multiply the respetive relative frequency by 360

what is 1 advantage of a stem and leaf plot

preserves the original data

what kind of data is a bar graph best used to display

qualitative

what type of data is a pie chart used to display

qualitative data

what type of data is a histogram used to show

quantitative data

with class width you should always

round up

benefits of dot plot

shows shape of data

side-by-side bar graph

two or more qualitative can be compared by viewing their bar graphs

T/f shape can be observed from histograms, frequency polygons, and stem-and-leaf-plots

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