Experimental Design

Steve wanted to see if different types of fertilizer influence sunflower growth. What is the explanatory variable?

• type of fertilizer

• sunflower grown without fertilizer

A student is planning an experiment to find out how the height from which he drops a ball affects how high the ball bounces. The response variable is the _____.

• Diameter of the ball

• Force acting on the ball

• Height that the ball bounces

• Height from which the ball is dropped

Can pleasant aromas help a student learn better? Two researchers believed that the presence of a floral scent could improve a person's learning ability in certain situations. They had 22 people work through a pencil-and-paper maze 6 times. Three of the times they wore a floral-scented mask and three times they wore an unscented mask. The three trials for each mask followed one another. Testers measures the length of time it took subjects to complete each of the six trials. They reported that, on average, subjects wearing the floral-scented mask completed the maze more quickly that those wearing the unscented mask, although, the difference was not statistically significant. This study is:

• convenience sample

• oberservational study

• experiment, but not double-blind

• double-blind experiment

Four groups of randomly selected people are assigned a different diet. After six months, the blood pressures of each group are compared.

• Observational Study

• Experiment

Match the following

• Completely Randomized Design

• Neither the subjects nor the members of the research team who interact with them know which

  treatment a subject is receiving.

• Matched Pairs Design

• Treatments are assigned completely at random within each block.

• Double-Blind Study

• A special case of a randomized block design. Using a blocking variable, subjects (whether they are people or not) are arranged in pairs matched on relevant factors.

• Single-Blind Study

• Treatments are assigned to experimental units

  completely at random.

• Randomized Complete Block Design

• Subjects do not know which treatment they are receiving, but members of the research team do, or vice versa.

Match the following:

• Treatment

• Different conditions

  assigned to experimental units.

• Population

• A treatment with an inactive substance

• Experimental Unit

• The individuals

  (which may be people or other objects of

  study) that are assigned treatments.

• Placebo

• A collection of experimental

  units either not given a treatment of interest or

  given a treatment with an inactive substance

• Control

• The complete set group of individuals

The tablecloths washed without bleach is the _____ group

• independent variable

• Dependent variable

• Experimental group

• Control Group

• Constants

A market research company wishes to find out whether the population of students at a university prefers Starbucks or Dunkin Donuts. A random sample of students is selected, and each student is asked first to try both but the order they try them is randomly decided with a coin toss (heads: Starbucks, then Dunkin. tails: vice versa). They then indicate which brand they prefer. This is an example of

• completely randomized experiment

• observational study

• stratified sample

• matched pairs experiment

In the previous problem, supposed that the researchers suspected that women over the age of 55 may respond differently to the treatment. Given that a random sample of 40,000 women over the age of 45 has already been chosen, the study would have been improved by:

• a stratified sample, with strata determined by age.

• a stratified sample, with strata determined by gender.

• a block design, with blocks determined by age.

• a block design, with blocks determined by gender.

• a double-blind completely randomized design.

What kind of experiment is shown in the picture?

• Randomized Block Design

• Completely Randomized Design

• Matched Pairs

• SRS