Replication

________: A good experiment uses enough experimental units in each treatment group to reduce chance variation.

random assignment of treatments

We can make an inference about cause- and- effect if we conducted a well- designed experiment with ________ and obtained statistically significant results.

Random assignment

________: A good experiment ________ treatments to subjects.

Dr Johnsons comment

________: Statistical significance does not require certainty that the observed effect was not due to chance; it just requires that the observed effect was unlikely to be the result of chance.

voluntary response bias

In ________, the researcher does not pick the sample.

real effect

The purpose of giving one group a placebo is to provide a basis of comparison to measure the ________ of the treatment.

Simple random sampling

________ does not reduce bias from poorly worded questions, under coverage, non- response, or other non- sampling errors.

The subjects that were given treatment A responded differently than the subjects who were given treatment B.  Dr. Johnsons comment

A difference in response is not enough

Dr. Johnsons comment

Statistical significance does not require certainty that the observed effect was not due to chance; it just requires that the observed effect was unlikely to be the result of chance

Random assignment

A good experiment randomly assigns treatments to subjects

Control

A good experiment controls for outside factors (confounding variables)

Compare

A good experiment compares the results (the response variable) for two or more treatments

Replication

A good experiment uses enough experimental units in each treatment group to reduce chance variation

Question

Suppose there are 2800 students at CHS

Answer 1

Give everyone a number, generate 50 random numbers

Dr. Johnsons comment

I am looking for precise number assignment and clear instructions on randomization

Answer 2

Every student can be associated with a number, and then the generator can decide the students based on the number it randomly picks

Dr. Johnsons comment

The calculator doesnt pick the students

Best answer

Give each student a distinct integer label from 1 to 2800

Dr. Johnsons comment

In the students answer, the procedure for randomization must be fully described so that two knowledgeable statistics users would, following the students instruction, use the same method to randomize

Question

Rather than using a completely randomized design, one group of CHS administrators proposes stratifying by political affiliation (democrat or republican)

Answer 1

They need to create a homogenous group, so there are not drastic differences

Dr. Johnsons note

This answer lacks context

Answer 2

Stratifying by political affiliation will create groups where the people in them will most likely have similar views to each other

Dr. Johnsons note

Stratified random sampling works best when the individuals within each stratum are similar with respect to what is being measured and when there are large differences between strata

My answer

The goal of stratification is to create homogeneous groups