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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