UNIT 3 PART B

Question 1

What do observational studies and experiments have in common?

Answer 1

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

Question 2

What is wrong with using voluteers in an experiment?

Answer 2

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 3

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

Answer 3

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 4

What’s the difference between lurking and confounding?

Answer 4

Lurking variables (weather impacts ice cream and surf accidents) are in studies infer the assoiation between the two varibles; confounding variables (sunlight you didn’t notice) are in experiments may make it seem like the treatment was effective, when in fact, it was the counfounding variable. In the end, you are confounded, Was it the sun or the fertilizer?

Question 5

How are voluntary and convenience samples similar?

Answer 5

With voluntary, people choose them selves, with covenience, the people are just chosen by researcher, neither uses randomness and both are prone to BIAS.

Question 6

Can you stratify in an experiment?

Answer 6

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

Question 7

name 2 differences between observational studies and experiments

Answer 7

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

Question 8

Explain two types of experimental design.

Answer 8

1.)Randomized Block Design: randomization occurs within the blocks only. 2.) Completely Randomized Design: all of the experimental units have the same chance at recieving a treatment.

Question 9

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

Answer 9

The two are similar because they divide the subjects into homogenous groups where the subjects are all similar

Question 10

How is clustering and stratifying different when doing a sample?

Answer 10

Clustering is when chosen at random a group from the population that looks like the population, clusters should be heterogenous. While Stratifying is slicing a population into homogeneous groups(strata). Then randomly sample within each stratum before the results are combined.

Question 11

5 INGREDIENTS TO EXPERIMENTS

Answer 11

control , randomization, replication. Compare and…Use blocking when appropriate

Question 12

What is a control group?

Answer 12

The group that doesn’t get a treatment. It helps us see the impact of the environment.

Question 13

What is a factor?

Answer 13

A variable in an experiment that the experimenter manipulates (like sleep)

Question 14

What is a level in an experiment?

Answer 14

A level is a specific value(s) that the experimenter chose for a factor that is manipulated.ex. Factor is sleep, level(s) would be how many hours the subjects were aloud to sleep.. 4 hours, 6 hours, 8 hours.. 3 levels

Question 15

What is bias?What are some common errors?

Answer 15

It’s any systematic flaw of a sampling method that make the results unreliable. COMMON ERRORS: Voluntary response, undercoverage of the population, nonresponse bias and response bias. We use randomness and methods like stratifying to reduce these.

Question 16

What is Placebo used for?

Answer 16

Placebo is used for control in an experiment. the purpose of placebo is to make sure each group has the same experience whether they are in the control group or not. (so both groups take pills).

Question 17

what is the best way to reduce bias?

Answer 17

randomness. sophisticated answer: make as many things as random as possible

Question 18

What is the difference between a study and an experiment?

Answer 18

In a study you are basically just watching and in an experiment you are manipulating factors and (hopefully randomly) assigning treatments

Question 19

What is the difference between confounding and lurking?

Answer 19

Confounding is to experiment, it may seem as both factors affect the response.Lurking is to sample, y and x makes it appear that x may be causing y

Question 20

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

Answer 20

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 21

What is the main purpose of a placebo ?

Answer 21

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 22

What is the placebo effect?

Answer 22

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

Question 23

What is the purpose of matching?

Answer 23

Matching, like blocking, reduces unwanted variation. In a retrospective or prospective study, subjects who are similar in ways not under study may be matched and then compared with each other on the variables of intrest.

Question 24

What is the sure way to assign treatments correctly?

Answer 24

throw names in hat and pick.. Or number subjects and randint

Question 25

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 25

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

Question 26

Who can be blinded?

Answer 26

1. Subjects (and dog owners..) 2. Those delivering treatments and Those assessing effectiveness of treatments. and three mice.

Question 27

Why do you have to block?

Answer 27

You don’t have to.. But you might want to if you feel that the experimental units (subjects) may respond differently to the treatment.

Question 28

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

Answer 28

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 29

Why randomize in an experiment?

Answer 29

To avoid bias. An experimenter might want their treatment to work, so may chose the subjects that might respond best.