unit 2: describing and comparing distributions

What are distributions shaped like?

Some are symmetrical with data distributed evenly about the mean, others are skewed, with data tending to the left or right of the mean

Tails

Found on skewed distributions, it is found opposite of where most of the data is located

What happens if you find tails at both ends?

It means the data is pretty symmetrical

What does the tail tell you about which way you’re skewed?

When you are left tailed, you also tend to be skewed to the left, and when you are right tailed you tend to be skewed to the right

What do the dots on the box-and-whisker plot mean?

Left most point is the minimum and the right-most point is the maximum

What is the line drawn inside the box of the box-and-whisker plot?

The median

What does the box in the box-and-whisker plot denote?

The middle 50% of the numbers

How can a box-and-whisker plot tell you which way the data is skewed?

Whatever side is opposite the box would be the tail

Outlier

A data point that is found far away from the rest

Cluster

A group of data points found in the same area

Further requirements to define an outlier

Cannot be connected to the rest of the data, it must be very separate on the graph

Peak

Found at the bucket or category with the most data points, looks like a mountain top

What are dot plots and box plots useful for?

Finding the median

What are histograms useful for?

Showing the number of values within a specific range

Why aren’t histograms good for finding the median?

They don’t give the exact data, it's all lumped into buckets

How do you find the median in a box plot?

The middle line explicitly denotes the median

Example of when histograms are useful

You want to know how many cars have more than 200k miles on them

When comparing distributions, what do people often talk about?

The center and the spread/variability

What will the ideal distribution allow for?

You want to be able to eyeball it instead of counting it out