Tricky weird bits

Question 1

Confidence interval definition (eg ‘What does a 95% confidence interval represent?’)

Answer 1

In repeated sampling, 95% of all intervals constructed this way will contain the true mean

Question 2

What is meant by a ‘5% Significance Level’?

Answer 2

There is a 5% chance of rejecting the null hypothesis, when it is in fact true

Question 3

Why is a paired test sometimes appropriate?

Answer 3

Because sometimes there are clear differences between individuals in a sample, and a paired test eliminates these differences

Question 4

What is the advantage/disadvantage of using a higher percentage (ie larger ‘k’) confidence interval?

Answer 4

Advantage: A higher % interval is more likely to contain the true mean

Disadvantage: The interval is less precise/wider

Question 5

What is ‘the standard error’ of a sample of size n with standard deviation s?

Answer 5

s/root n