If you're seeing this message, it means we're having trouble loading external resources for Khan Academy.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Comparing and sampling populations

4 videos
3 skills
When we are trying to make a judgement about a population, it is often impractical (or impossible) to observe every member of the population. Imagine trying to survey all 300+ million Americans to understand the likely outcome of the next presidential election! Because of this, much of statistics is collecting data from a representative and random sample. From the data collected from this random sample we can infer things about the greater population.

Inferring population mean from sample mean

VIDEO 10:03 minutes
Much of statistics is based upon using data from a random sample that is representative of the population at large. From that sample mean, we can infer things about the greater population mean. We'll explain.

Reasonable samples

VIDEO 4:17 minutes
To make a valid conclusion you'll need a representaive, not skewed, sample

Valid claims

PRACTICE PROBLEMS

Mean absolute deviation word problem

VIDEO 5:46 minutes
Here's a word problem where we show you how to calculate the mean absolute deviation in order to compare two distances.

Dot plot and distribution word problem

VIDEO 4:00 minutes
Let's examine the distribution of a dot plot to draw conclusions about the times of Olympic swimmers.

Comparing populations

PRACTICE PROBLEMS

Variation in samples

PRACTICE PROBLEMS