Module 04 Summary

What this module established

Every sample from the same population gives a different answer, and the spread of those answers is the whole subject. Five samples of 30 landed up to 36 away from a population mean of 500; across 1000 samples the spread was 18.

Carry forward

• The distribution of the data and the distribution of the mean are different things. A strongly skewed population still gives a symmetric, narrow sampling distribution at n = 200.
• SD describes the spread of values; SE describes the spread of the estimate and falls with the square root of n. Halving it again costs four times the data.
• The bootstrap gives an interval for statistics with no formula — a median's interval came out 21.23 to 39.13 with no textbook needed.
• The 95% belongs to the procedure. Of 1000 intervals, 947 contained the truth; any one of them either does or does not.

Before moving on

Move on when you can explain why 'there is a 95% chance the true mean lies in this interval' is wrong, and say what is right instead.

Mark complete