MIDTERM 1

Question 1

WHAT ARE THE 4 METHODS FOR COLLECTING DATA?

Answer 1

1. DESIGN EXPERIMENT
2. OBSERVATIONAL STUDY
3. SAMPLING SURVEY
4. CLINICAL TRIALS

Question 2

What is the process of doing an experimental design?

Answer 2

• specify the treatment, response, experimental unit
• assign treatments to the unit
• observe the response, the causal effect
• need techniques to control the uncontrollable factors

Question 3

What is an observational study?

Answer 3

• treatments are simply observed as belonging to the unit
• may not be causal
• causal effect may not be clear, may need specific methodology to find the causal effect
• retrospective and prospective

Question 4

What is a sampling survey?

Answer 4

• a physical population of units
• we select a sample from the population, collect data from the sample
• sample is assumed to be representative of the pop.
• estimate the population features using the sample
• we can detect association, but not a causal effect

Question 5

What are clinical trials?

Answer 5

• similar to a design experiment
• for humans, many treatments allocations are not feasible
• specific designs

Question 6

What are the objectives of a statistical experiment?

Answer 6

• determine which factors are most influential on the response
• determine where to set the influential factors so that: 1. the outcome is close to the designs nominal values ? and 2. the effects of the uncontrollable factors are minimized

Question 7

What are the 3 key elements of a stats experiment? describe them

Answer 7

1. Experimental unit - the unit that you can apply the treatment to
2. Treatment options - what options we apply to the units
3. Response measurement - what is the outcome of interest?

Question 8

Review: Hotelling’s elegant design

Answer 8

ok

Question 9

When the problem involves data that are subject to experimental errors ….

Answer 9

we must use statistical methodology for the analysis

Question 10

Design: How we collect the data and Analysis: …

Answer 10

need to ensure that all assumptions are valid and that we collect data in a manner that ensures analysis assumptions are valid

Question 11

What are the 3 basic principles for stats exp. design ?

Answer 11

1. randomization 2. repitition 3. blocking

Question 12

What is randomization?

Answer 12

when we allocate the treatments in a completely randomized way and the order in which experiments are performed is random

Question 13

When we use randomization, what can we do? 4

Answer 13

• make assumptions about independence of obs
• make each possible assignment equally likely
• avoid systematic error/bias
• aveerage out the effects of extraneous factors

Question 14

What is replication?

Answer 14

• Repitition of the basic experiment - change the unit each time

Question 15

Why is replication important? 2

Answer 15

• allows us to estimate the experimental error
• gives us a more precise estimate of the effect of interest

replication > repeated measurements (estimate the measurement error)

Question 16

what is blocking?

Answer 16

a technique that is used to improve the precision with which comparisons of the factors of interest are made

Question 17

what is the goal of blocking?

Answer 17

create a set of relatively homogeneous experimental design conditions so the experimental units are are homogeneous as possible

Question 18

why is blocking used? what does it reduce?

Answer 18

the variability from nuisance factors

Question 19

what are nuisance factors?

Answer 19

they are factors that have effects on the response