________: A good experiment uses enough experimental units in each treatment group to reduce chance variation.
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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.
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Random assignment
________: A good experiment ________ treatments to subjects.
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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.
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voluntary response bias
In ________, the researcher does not pick the sample.
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real effect
The purpose of giving one group a placebo is to provide a basis of comparison to measure the ________ of the treatment.
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Simple random sampling
________ does not reduce bias from poorly worded questions, under coverage, non- response, or other non- sampling errors.
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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
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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
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Random assignment
A good experiment randomly assigns treatments to subjects
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Control
A good experiment controls for outside factors (confounding variables)
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Compare
A good experiment compares the results (the response variable) for two or more treatments
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Replication
A good experiment uses enough experimental units in each treatment group to reduce chance variation
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Question
Suppose there are 2800 students at CHS
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Answer 1
Give everyone a number, generate 50 random numbers
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Dr. Johnsons comment
I am looking for precise number assignment and clear instructions on randomization
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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
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Dr. Johnsons comment
The calculator doesnt pick the students
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Best answer
Give each student a distinct integer label from 1 to 2800
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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
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Question
Rather than using a completely randomized design, one group of CHS administrators proposes stratifying by political affiliation (democrat or republican)
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Answer 1
They need to create a homogenous group, so there are not drastic differences
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Dr. Johnsons note
This answer lacks context
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Answer 2
Stratifying by political affiliation will create groups where the people in them will most likely have similar views to each other
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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
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My answer
The goal of stratification is to create homogeneous groups
Studied by 1 person
