DECK 8: UNIT 3 PART B (experiments and studies)

Question 1

What is the sure way to assign treatments correctly?

Answer 1

throw names in hat and first half in group 1 and the rest group 2. . Or number subjects from 1-n and use randint until you get half for group 1.

Question 2

How are we using random numbers in experiments vs studies?

Answer 2

In a study, we randomly choose subjects to survey from the population as a whole. In an expermint we randomly assign subjects to treatment groups

Question 3

How are we making inferences differently in experiments vs studies?

Answer 3

In observaional studies, you make and inference about the population, in an experiment you make an inference about a treatment.

Question 4

How are we manipulating the environment differently in experiments and studies?

Answer 4

No manipulation or treatments in an observational study. You only manipulate environment in an experminet.

Question 5

How are we proving causation in experiments and obs studies?

Answer 5

No causation in a study, maybe association or correlation. ONLY EXPERIMENTS SHOW CAUSATION.

Question 6

How do we use representative samples in experiments and studies?

Answer 6

You don’t need a representative sample in an experiment. You are not making inferences about a population, just about a treatment.

Question 7

What is the difference between confounding and lurking?

Answer 7

Confounding is in experiments, like sunlight confounding a fertilizer experiment. Lurking is when you think hot chocolate causes ski accidents. “lurking”is actually a word not even used in AP STATS.

Question 8

What is wrong with using voluteers in an experiment?

Answer 8

Not much. In an experiment, we are not looking for a sample that is like the population. We just want to see the effectiveness of a treatment. It is fine if the subjects are all similar. In fact it is best sometimes when they are!

Question 9

What is a control group?

Answer 9

The group that doesn’t get a treatment (or gets the old treatment). It helps us see the impact of the environment. It gets the placebo or standard care but goes through all of the motions

Question 10

Give example of confounding variable.

Answer 10

fertilizer A vs B. If you have two tables in a room with tomato plants and and one table gets A and the other gets B, but later you realize that the table with A was near the windows. You say that SUNLIGHT IS A CONFOUNDING VARIABLE in that experiment.

Question 11

In the fertilizer experiment, how could you plan to eliminate the confounding variable?

Answer 11

USING RANDOMIZED BLOCK DESIGN. Make each table a block, and then randomly assign fertilzer A and B to the plants at each table. Compare the fertilizers for table 1, then compare the fertilizers on table 2.

Question 12

Why does it make sense to double-blind an experiment?

Answer 12

It reduces bias in an experiment. If subjects don’t know what treatment they’re receiving, they won’t change their habits based on that knowledge. If evaluators don’t know which treatment each subject is receiving, they won’t bias the true results based on the results they expect to see

Question 13

4 INGREDIENTS TO EXPERIMENTS

Answer 13

Compare, control , randomization, replication (and BLOCKING when you need to)

Question 14

4 ingredients: What is “compare?”

Answer 14

Having something to compare your treatment with helps you see its effectiveness.

Question 15

4 ingredients: What is “control?”

Answer 15

You want to control the environment as best as you can so that the only difference between groups is the treatment, and the treatment only. Everything else should be similar.

Question 16

4 ingredients: What is “BLOCKING?”

Answer 16

If you think different groups of subjects may respond differently to treatments because of location, gender, age, then you make BLOCKS, and make sure to compare the treatments within each block.

Question 17

4 ingredients: What is “replication?”

Answer 17

Having plenty of subjects in each treatment group. You don’t want to test fertilizer on just one plant.

Question 18

4 ingredients: What is “randomization?”

Answer 18

You want to randomly assign subjects to treatment groups.

Question 19

What are the two (three) types of experiments?

Answer 19

1. Completely randomized 2. Randomized block (matched pairs)

Question 20

What is the difference between a completely randomized and a randomized block?

Answer 20

In a completely randomized experiment, all of the subjects names go into ONE HAT and you pick for treatment groups. In a randomized block design you have more hats (a hat for males, a hat for females etc) and pick for treatments from each.

Question 21

Give example of a matched pair design study for fuel efficiency

Answer 21

Testing fuel efficiency of different gasolines. Subjects use both fuel A for a month and fuel B for a month and compare, based on their driving habits and vehicle, which was more efficient. BE SURE TO RANDOMLY CHOOSE WHICH ONE GOES FIRST FOR EACH SUBJECT.

Question 22

Give an example of matched pair design for comparing a new blood pressure medication to an older version?

Answer 22

Have subjects use the new medication for a month and the old one for a month and compare. Be sure to randomize which month and blind.

Question 23

What is the placebo effect?

Answer 23

When those who get the placebo show improvements, or show the effects of the treatment. This often happens to up 20% of participants!

Question 24

Who can be blinded? ( two groups)

Answer 24

1. Subjects (and dog owners..). The poeple getting treatment and 2. administrators. Those delivering treatments and assessing effectiveness of treatments.

Question 25

What is statistically significant?

Answer 25

When an observed difference is too odd for us to believe that it is likely to have occurred naturally (or just randomly). Basically it is Statistically Significant when we don’t think it happened randomly. when you think “something’s up” or “something’s fishy”

Question 26

What is difference between subject and experimental unit?

Answer 26

Humans who are experimented on are commonly called subjects in an experiment. Subjects like dogs, days, plants and anything not human are called Experimental Units

Question 27

What is the purpose of matching?

Answer 27

it isolates the differences between subjects so help see the impact of the treatment.

Question 28

What “designs” are there for experiments?

Answer 28

completely randomized, random block, and matched pair design(type of block)

Question 29

What is a factor? give example

Answer 29

DIET PLAN would be a factor and levels could be: low carb, low fat, and no diet

Question 30

What do observational studies and experiments have in common?

Answer 30

In both, you are making OBSERVATIONS.. recording data… doing statistical analysis…

Question 31

What’s a useful alternative when you can’t run an experiment? What are they useful forms of this, and how do you preform them respectively?

Answer 31

An alternative of an experiments could be an observational study. t.

Question 32

Give example of randomized block design for a new anxiety med vs placebo with 100 volunteers (60m and 40f)

Answer 32

Block by gender. Randomly assign 30m to new and rest placebo. Randomly assign 20w new and rest placebo.

Question 33

How is Blocking in an Experiment Similar to Stratefying in a Sample?

Answer 33

The two are similar because they divide the subjects into homogenous groups where the subjects are all similar (these traits were already present in the population)

Question 34

What type of study would find relationship beween Verbal and Math SAT?

Answer 34

You could take all of the SAT Math and Verbal scores and run a regression and find the r-quared value and linear model. This would be a Retrospective Study.

Question 35

What is the main purpose of a placebo ?

Answer 35

To blind the subject that is being experimented on to avoid influence to the given variable therefore altering the response variable . When people think they’re getting help, they often improve anyway..

Question 36

What is matched pair design?

Answer 36

A type of blocking where you match subjects to other “like” subjects… MOST OFTEN SEEN WHEN YOU COMPARE A SUBJECT TO ITSELF!! (like pre-post tests)

Question 37

Why randomize in an experiment?

Answer 37

To reduce confounding variables (and bias).

Question 38

What is difference between completely randomized and random block design?

Answer 38

Completely randomized takes all units and puts them in a hat and randomly chooses treatments, blocked puts them all in different hats first (blocks) and then chooses

Question 39

What is the difference between single-blind and double blind?

Answer 39

Single blinding is when all individuals in either one of the classes are blinded; double-blinded is when everyone in BOTH classes are blinded. Classes are: subjects and the other is treatment givers + evaluators…

Question 40

Can you stratify in an experiment?

Answer 40

NO. stratification is a sampling method, blocking is method used in experiments. They are similar ideas.

Question 41

name 2 differences between observational studies and experiments

Answer 41

1. Experiments can prove causation (studies can’t) . 2. In experiments, you assign treatments (studies you just watch)

Question 42

What is a level in an experiment? give example

Answer 42

Example. For the Factor “SLEEP” the, level(s) would be how many hours the subjects were alowed to sleep.. 4 hours, 6 hours, 8 hours.. 3 levels

Question 43

Give example of factors and levels

Answer 43

Factor: medication. Levels: 50mg, 100mg and 200mg.

Question 44

Suppose you are doing a weight loss experiment with 2 diets (A. low carb and B. low fat), and three medications (1. NUTRI LOSS, 2. POUND DROPPER and 3. SLIMMERLY). How many treatment groups would there be?

Answer 44

there would be 6: A1, A2, A3, B1, B2, B3

Question 45

Suppose you are doing a weight loss experiment with 2 diets (A. low carb and B. low fat), and three medications (1. NUTRI LOSS, 2. POUND DROPPER and 3. SLIMMERLY). What is the response variable?

Answer 45

weight loss (pounds)

Question 46

If you randomly choose subjects from the population what can you make an inference about?

Answer 46

You can make and inference about the population, you can talk about an association, but not about causation.

Question 47

If you randomly assign subjects to treatment groups, what can you make an inference about?

Answer 47

You can make an inference about the treatment, about cause an effect.