Choosing a statistical chart

The chart that suits each type of variable: bars, sticks, histogram, cumulative frequency polygon, box plot, scatter plot.

The outline, topic by topic

Each topic is weighted the way the exam weighs it.

Bar chart: what is it?
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A representation of a qualitative variable by separate bars, whose height is proportional to the count or the relative frequency of each category.
The bars are spaced because the categories are distinct, with no value in between; their order is free for a nominal variable.
A histogram has a class [30, 100) holding 70 requests. What height should its rectangle have?
- 1 request per ms
- 70 requests
- 0.7 request per ms
- 35 requests per ms
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1 request per ms
Height = count / width = 70 / 70 = 1 request per ms. 70 forgets to divide by the width, 0.7 divides by the bound 100, 35 divides by 2.
In a histogram whose classes have unequal widths, it is the … of the rectangles, not their height, that is proportional to the count.
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In a histogram whose classes have unequal widths, it is the area of the rectangles, not their height, that is proportional to the count.
A class twice as wide holding the same number of individuals must have a rectangle half as tall, otherwise it would look twice as crowded.