Experiments Justin Weinstock STAT 2120

Question 1

• In an observational study, we measure

Answer 1

In an observational study, we measure individuals in the sample
without trying to affect them.

Question 2

In an experiment,

Answer 2

In an experiment, the statistician sets the levels of the explanatory
variable

Question 3

What is the benefit of carrying out an experiment compared to an
observational study?

Answer 3

When we choose carefully how the levels of the explanatory variable
are assigned to our sample, we can actually determine a cause-and-
effect relationship between the explanatory and response variable!

Question 4

• The experimental design is defined by four principles:

Answer 4

1. Control
2. Replication
3. Blocking
4. Randomness

Question 5

Experimental unit:

Answer 5

one member of the initial sample that will be
subjected to the experiment

Question 6

The explanatory/independent variables are commonly referred to as

Answer 6

factors

Question 7

Each factor has multiple levels.

Answer 7

The levels or treatments of a factor are the
chosen values of the factor that are being varied in the experiment

Question 8

We often refer to the group of experimental units assigned to a treatment as
a

Answer 8

treatment group

Question 9

The act of applying the explanatory variable levels to more than one
subject is called

Answer 9

replication.

Question 10

For other variables that we expect to affect our response variable
(resting heart rate) – we call these nuisance factors or confounding
factors

Answer 10

we want to ensure that the distributions of these variables
are identical between the supplement and the placebo groups.

Question 11

A block is a group of subjects

Answer 11

A block is a group of subjects known to be similar in some way that is
thought to influence the response variable.

Question 12

Assignment of subjects to groups (supplement vs. placebo) should be
carried out

Answer 12

randomly