In order to see which variety of apple tree produces more fruit, a farmer sets up an experiment. He has three plots of land with different soil and natural water availability. Each plot has room for eight trees.
The farmer randomly selects four locations in each plot for the first variety of tree and the other four get the second variety. This experiment is
A) completely randomized with one factor: the variety of tree
B) randomized block, blocked by plot of land
C) completely randomized with two factors
D) randomized block, blocked by variety of tree
E) completely randomized with one factor: the plot of land
Q. 2It was discovered that a larger proportion of children who slept with nightlights later developed nearsightedness, compared to children who did not sleep with nightlights.
The headlines read, Leaving a light on for you children causes nearsightedness Later it was pointed out that nearsighted people have more trouble seeing in the dark and are more likely to leave lights on at night for their kids. And those same nearsighted parents are likely to have nearsighted kids. This is an example of
A) a randomized block design.
B) a placebo.
C) a lurking variable.
D) bias.
E) a control group.
Q. 3A Columbia University study linked soda consumption to behavior problems in children. Researchers examined data from a previous study that followed 2929 mother-child pairs.
One survey asked about behaviors of the child and also about soda consumption. They found that the more soda the kids drank, the more behavior problems they had. What aspect of a well-designed experiment is absent from this study?
A) a control group
B) randomization
C) blinding
D) a placebo
E) all of these
Q. 4In an experiment the primary purpose of blocking is to
A) reduce the within-treatment variation.
B) reduce the between-treatment variation.
C) eliminate the need for random assignment of treatments.
D) eliminate confounding variables.
E) reduce bias.
Q. 5A company has tried to improve the effectiveness of its dishwashing detergent and wants to see if it works better than the original formula. They use 6 identical new dishwashers and load them identically with dirty dishes.
Three packs of each of the two types of detergent are used, and they are randomly assigned to one of the six dishwashers. After the load is run, they rate each load for overall cleanliness. Which of the following is true?
A) Blinding is impossible in this experiment because they must be able to see the dishes.
B) The explanatory variable is the different dishwashers.
C) Because each brand is used in three dishwashers, replication is used properly.
D) A control group with no detergent at all is needed.
E) The response variable is the type of detergent.
Q. 6Does Procellera Antimicrobial Wound Dressing help injuries heal faster? Researchers checked records of 38 patients who had been treated for acute or chronic wounds between 2010 and 2012.
They found that those who had been treated with Procellera healed almost twice as fast. This is a
A) matched experiment
B) prospective study
C) retrospective study
D) survey
E) randomized experiment
Q. 7A school district administrator sent a survey to all teachers in the district. Only 30 of the teachers responded to the survey. Which of the following is true?
I. The people that did not responded are likely to be similar to those that did so he should use them as the sample.
II. This survey design suffered from non-response bias.
III. Because he sent the survey to everyone, this is a census and the results can be applied to the whole population.
A) II only
B) I, II, and III
C) I only
D) I and II only
E) II and III only
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