Experimental Designs Practice (Statistics)

Left-handedness is the preference for the left hand over the right for everyday activities such as writing. Studies indicate that about 93% of the population may be characterized as right-handed. Researchers would like to conduct a study to determine if left-handed teens differ significantly in their ability to memorize facts than right-handed teens.

The explanatory variable in this study is:

• ability to memorize facts.

• age.

• handedness.

• researchers.

• none of the above.

Researchers were interested to know whether internal vehicle temperatures vary by outside temperatures. To evaluate this, temperature rise was measured continuously over a 60-minute period in a dark SUV on 16 different clear, sunny days with outside temperatures ranging from 72^oF to 96^oF.

What type of study is this?

• a census.

• a survey.

• an observational study

• an experiment

Researchers want to know how diet influences a child's brain development. In a sample of 100 5 year old children, 20 of the children are given a vegan diet, 20 are given a pescatarian diet, 20 are given a standard American diet, and 20 are given a paleo diet.

This is an example of...

• a matched pair, with pairs determined by diet type

• a block design, with blocks determined by age.

• a block design, with blocks determined by diet type.

• a completely randomized experiment

The Women's Health Study randomly assigned nearly 40,000 women over the age of 45 to receive either aspirin or a placebo for over 10 years to examine the effect of aspirin on cancer risk to healthy women.

This is an example of...

• a survey

• an observational study

• a completely randomized experiment

• a blocked experiment

• a matched pair experiment

Dentists want to know if a fluoride mouth wash will help prevent cavities. After 6 months, they will compare the number of cavities in those who used the mouth wash versus those who did not.

Which is an example of a matched pairs design for this experiment?

• Dentists sort 40 patients into groups based on age, such as 10-14, 15-20, 21-26, and 26-30. Half of the patients in each group are given the mouth wash, half are not.

• Dentists sort 50 patients into pairs that are the same age. 1 person is given the mouth wash and 1 is not.

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 custodian notices some dirty tables and wants to know which cleaner is more effective. He tests three different cleaners and looks at how well they clean compared to tap water. What is the explanatory variable?

• type of cleaner

• tap water

Mrs. Barton wanted to see how different types of music affected students' pulse rates. She played different types of music: heavy metal, rap, R&B, alternative, pop, country, and classical music. Identify the response variable. 

• pulse rate
• types of music
• classical music resulted in the highest pulse rate
• Mrs. Barton

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

What is the purpose of a control group in an experiment?

• To provide a standard for comparison

• To introduce new variables

• To ensure the experiment is biased

• To change the outcome of the experiment