# Inference comparing two groups or populations

AP®︎ Statistics,

If a poll from one location shows 55% of voters support a measure, but a poll from another location shows 45% support, does that mean there is a difference between the two populations? We can make a confidence interval to estimate the difference, or do a significance test to see if the difference is significant. We'll use similar methods to compare the means of two groups.

This course contains 4 segments:

Confidence intervals for the difference between two proportions

We can build a confidence interval to estimate the difference between two population proportions. For example, a politician might poll samples of people from two different locations to estimate the difference in the percent of voters that support their campaign.

Testing the difference between two proportions

We can do a significance test to judge if the difference between two proportions is significant (unlikely to occur by chance alone). For example, a company might want to test to see if there is a difference in what percent of their employees are satisfied between two of their locations.

Confidence intervals for the difference between two means

We can build a confidence interval to estimate the difference between two population means. For example, a food scientist might want to estimate the difference in the average sizes of two varieties of the same fruit.

Testing the difference between two means

We can do a significance test to judge if the difference between two means is significant (unlikely to occur by chance alone). For example, a chain of restaurants might want to test to see if there is a difference in the average portion size between two of their locations.

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