Worksheet: Experimental Studies

In this worksheet, we will practice identifying the types of an experimental study and differentiate between its variables.

Q1:

A solar panel manufacturer plans to carry out an experiment to investigate how two different transparent protective coatings deposited on solar panels affect their efficiency.

Which of the following is the treatment variable in this experiment?

  • Asun exposure
  • Bsolar panel efficiency
  • Cweather conditions
  • Dtransparent protective coating
  • Eprotective coating thickness

Which of the following is the response variable in this experiment?

  • Asolar panel efficiency
  • Bprotective coating thickness
  • Ctransparent protective coating
  • Dweather conditions
  • Esun exposure

Q2:

Which of the following statements about blocked experiments is NOT true?

  • ASubjects are homogenously grouped according to certain characteristics (or variables).
  • BSubjects are randomly assigned to a treatment group within each block.
  • CThe effect of the treatment variable is observed within each block.
  • DConfounding variables are taken into account by ensuring that the sample is representative of the whole population.
  • EBoth control and randomization are considered.

Q3:

Madison wants to redecorate her bedroom. She has found two different blue paints for the door. She wants to test which of them, once dry, gives the closest color to that of her bed frame.

Which of the following is the treatment variable in this experiment?

  • Adoor color
  • Bbed frame color
  • Cpaint type
  • Dtype of paintbrush
  • Etype of solvent

Which of the following is the response variable in this experiment?

  • Apaint type
  • Bbed frame color
  • Ctype of paintbrush
  • Ddoor color
  • Etype of solvent

Q4:

A real estate agency have found some volunteers to test two different website designs. They have grouped the volunteers in pairs so that, in each pair, both participants have the same characteristics in terms of gender, age, IT skills, and experience with property search. Then, they randomly assign one website to be tested to one participant in each pair and the other website to the other participant. What is this type of experiment design called?

  • Amatched-pair design
  • Bdouble-blind experiment
  • Cblocked experiment
  • Dblind experiment
  • Erepeated measures design

Q5:

Matthew wants to know if his new idea for a bread recipe will indeed improve his homemade bread. He invites a group of friends to a brunch at his house. He gives half of them the bread made according to the old recipe first and then the bread made with the new recipe, while the other half of his friends get the two different bread in the reverse order. What is this type of experiment design called?

  • Ablocked experiment
  • Brepeated measures design
  • Cmatched-pair design
  • Ddouble-blind experiment
  • Eblind experiment

Q6:

The owner of a fitness club wants to investigate whether eating a yogurt whose composition is specially designed for sports people increases their performance. She notices that the members of her club have different characteristics in terms of age and level of sports practice in general.

She wants to find out what proportion of her club’s members already eat this yogurt regularly by surveying a sample of members. She thinks a proportional stratified sample would be a suitable technique. Which of the following statements about her stratified sample is not true?

  • ASubcategories are defined by all possible combinations of age and level of sports practice.
  • BA random sample is produced from each subcategory.
  • CFor each subcategory, the sample size is a given percentage of the total number of members in this subcategory.
  • DA random sample is generated and then blocks are formed based on some subcategories.

The club owner now wants to investigate the effect of eating this ‘special’ yogurt. She sends an email to all her club’s members, calling for volunteers among people who have never tried this yogurt. No less than 76 members have volunteered. As she has identified age and level of sports practice as possible confounding variables, she groups her volunteers according to 12 subcategories given by four age groups and three levels of sports practice. She then randomly splits each group into two halves and gives to one of them a diet based on this yogurt and to the other half a diet based on a placebo (i.e., a ‘normal’ yogurt but with the same label as the previous one).

What is the treatment variable in this experiment?

  • Asports practice
  • Bsports performance
  • Cyogurt diet
  • Dage

The club owner used a measure of fitness performance before and after the diet and then analyzed how this measure changed with or without the ‘special’ yogurt for each subcategory. What is this type of experiment design called?

  • Astratified sampling
  • Brepeated measures design
  • Cblocked experiment
  • Dmatched-pair design
  • Edouble-blind experiment

Q7:

Education scientists thought of a new way to teach a certain topic. They decided to test the effectiveness of their method by teaching the topic in the traditional way to a given group of students and in the new way to another group of students and then compare the performance of both groups of students at a task related to the taught topic.

Many variables need to be controlled in order to make their experiment results valid. Which of the following variables does NOT need to be controlled?

  • Aage of the students
  • Bprior learning of the students
  • Cacademic level of the students
  • Dnames of the students
  • Eweekday and time of the lessons

Not telling the students that they are taking part in an experiment makes it a blind experiment. If they wanted to make a double-blind experiment, what would be necessary?

  • Athat the teachers do not know the students’ names
  • Bthat the teachers cannot see the students
  • Cthat the students have never seen the teacher before
  • Dthat the students are taught via videos
  • Ethat the teachers do not know they are using a new teaching method

Q8:

David wants to investigate whether mud on his sweater is better washed out when the stains are first rubbed with soap or when soaked overnight in clean water.

Which of the following is the treatment variable in this experiment?

  • Awashing program
  • Bwashing temperature
  • Ctype of soap
  • Dprewash treatment
  • Etype of laundry detergent

Which of the following is the response variable in this experiment?

  • Athe weight of the laundry
  • Bcleanliness level
  • Cdrying time
  • Ddrying conditions
  • Ethe smell of the laundry

Q9:

An experiment has been designed to investigate the alleged benefits of using a fabric softener. In the experiment the participants are divided into two groups: one group gets laundry washed using a fabric softener, while the other gets laundry washed without using any fabric softener. All of the participants laundry is washed over several weeks and none of the participants know how their laundry has been washed.

Which of the following is the type of the experiment?

  • ADouble-blind experiment
  • BRepeated measures design
  • CMatched-pair design
  • DBlocked experiment
  • ESingle-blind experiment

Which of the following is the treatment variable?

  • AUse of fabric softener
  • BSkin sensitivity
  • CWashing temperature
  • DColor of fabric
  • EType of fabric

Q10:

A drug company conducted a trial to find out if females aged 25–40 experienced an improvement in their migraine symptoms if they took a new drug. The people in the trial found that the number of migraines they experienced was halved.

Which of the following inferences would the company make from their results?

  • AThe drug halves the number of migraines in females.
  • BThe drug halves the number of migraines in females between the ages of 25 and 40.
  • CThe drug halves the number of migraines in people between the ages of 25 and 40.

Q11:

A pharmaceutical company wants to find out if a new drug can delay the formation of white hair. They decide to carry out an experiment using a placebo.

Which of the following is the treatment variable in this experiment?

  • ADrug treatment
  • BGender
  • CWhen white hair first appears
  • DShampoo used
  • EAge

Many variables need to be controlled in order to make the experiment results valid. Which of the following variables does not need to be controlled?

  • ADiet
  • BAge
  • CHeight
  • DAge at which the participant’s parents got white hair
  • EEthnicity

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