Principles of Statistical Interference

Question 1

What is statistical inference?

Answer 1

The process by which we draw conclusions about a population from data collected on a sample

Question 2

What is the estimand of a clinical trial

Answer 2

The treatment effect in question as defined at a population level

Question 3

What does uptake into the sample population of a clinical trial depend on?

Answer 3

Inclusion/exclusion criteria
Sites and patients that are willing
Financial and practical considerations on the number or geographical location of sites

Question 4

How do we denote the difference between population and sample parameters?

Answer 4

Population - represented with greek letters (mu or pi)

Sample - roman letters - x or p

Question 5

What are the three properties of a sampling distribution?

Answer 5

1. The mean of a large number of estimates obtained from samples of identical size is equal to the true population value
2. The standard deviation of the sampling distribution (the standard error) decreases as the sample size increases.
3. The shape of the sampling distribution is approximately normal when the sample size is large.

Question 6

What is the name of the standard deviation of the sampling distribution?

Answer 6

Standard error

Question 7

What does the standard deviation represent?

Answer 7

The variability in the original (individual) data

Question 8

What does the standard error represent?

Answer 8

The variability in repeated sample estimates

Question 9

How do you calculate the standard error?

Answer 9

SE (x bar) is equal to the standard deviation divided by the square root of the sample size

Question 10

What method of random sampling produces the smallest standard error?

Answer 10

Simple random sampling. Errors of other schemes are larger and depends on study design