Lecture 19- Two samples

Question 1

How do comparisons differ between a binary or continuous outcome?

Answer 1

• For a continuous outcome we compare means.

- For a binary outcome we compare proportions.

Question 2

If we have two random variables how do you compare the difference in the means?

Answer 2

-Choose two samples of size n1 and n2.
-Estimate the population difference in means, µ1 − µ2, with the
sample difference in means ¯x1 − x¯2.

Question 3

Do practise problem on slide 380

Question 4

What do you need to be careful of if your sample sizes are small?

Answer 4

-If the samples are very small, both populations should have values
which are normally distributed.
-In cases where the above assumptions aren’t met, a transformation of
the values may be useful, e.g. a log transform. In that case we could
work with the logs of the data.