chapter 2 Flashcards
what is a database?
a collection of information
what is data called that has 2 variables?
bivariate data
what does a pictogram use?
symbols or pictures to represent a number of items
in a bar chart…
- bars are equal widths with equal spaces between them
- the height (or length) of the bar represents the frequency
what is a vertical line graph?
similar to a bar chart- has lines instead of bars
what do multiple bar charts have?
more than one bar for each class
in a composite bar chart what does each bar show?
how the total frequency for that category is made up from different component groups
what does a stem & leaf diagram show?
numerical data- split into a “stem” and “leaves”
how are the numbers written in a stem & leaf diagram?
in order
what does the stem & leaf diagram show?
the shape of the data distribution
what does a back to back stem & leaf diagram show?
two sets of data with the same stem
on back to back stem & leaf diagram where are the smallest values on each row?
nearest to the stem
a pie chart is a way to display data in what way?
when you want to show how something is shared/divided
what does a pie chart use to represent frequency?
area
what do the angles at the centre of the pie chart add up to?
360 degrees
in a pie chart, what is the area of the sector proportional to?
proportional to the frequency of the category
what is the area of the pie chart proportional to?
the total frequency
if two sets of data have different frequencies and they were drawn the same size- why is this bad?
it is misleading
what are areas in comparative pie charts like?
the area of the 2 pie charts are in the same ratio as the two frequencies
what are comparative pie charts used for?
to compare 2 sets of data
how to compare the total frequencies of comparative pie charts?
compare the areas
how to compare the proportions of comparative pie charts?
compare the individual angles
what are population pyramids similar to?
bar charts or stem and leaf diagrams
what do population pyramids show?
the age groups in a population- usually divided by gender
what is a choropleth map used for?
used to classify regions of a geographical areas
in choropleth maps how are regions shaded?
with an increasing depth of colour
why is a key required in choropleth maps?
to show what each shade represents
a choropleth map can also be….
a diagram instead of a map
what is a histogram similar to?
a bar chart
what type of data do histograms use?
continuous data
why are there no gaps between the bars in histograms?
because the data is continuous
what does a frequency polygon do?
joins the mid-points of the top of the bars with straight lines
what is cumulative frequency?
a running total of frequencies
when would a cumulative frequency step polygon be used?
for discrete data
when would a cumulative frequency diagram be used?
for grouped continuous data
with a cumulative frequency diagram, how do you join the points?
with a smooth curve
what can cumulative frequency diagrams be used for?
to estimate or predict other values
what does a histogram show about the data?
how the data is distributed across the class intervals
what direction will positive skew be in?
-> ( going right)
what direction will negative skew be in?
<- (going left)
what do you need to do when drawing a histogram with unequal class intervals?
need to adjust the height of the bars so that the area of the bar represents the frequency
with histograms with equal class intervals, what represents the frequency?
the height
in histograms with unequal class intervals what represents the frequency?
the area of the bar
how to figure out frequency density?
frequency/class width
when can you compare data in histograms?
- if they have the same class intervals
- if they have the same frequency density scales
what are some features of misleading diagrams?
- scales that do not start at zero
- lines on a graph that are too thick to interpret information
- graphs and charts without keys may be misleading
why do 3D diagrams make comparisons difficult?
- things at the front of the diagram can appear larger than those at the back
- sections from the diagram separated from other parts make comparisons difficult
what do bar charts and line graphs show?
trends and patterns in data
