Freshman Statistics Seminar

Week 10:Hypothesis Testing and Experimental Design

David Schladt

Class Goals:

  • Understand the difficulties in designing an experiment to test an hypothesis
  • Gain experience in designing experiments to test specific hypotheses

Class Outcomes:
By the end of the class, students will be able to:

  • Design a basic outline of an experiment to test a specific hypothesis

Article Summary:

  • Anon 2006 Reuters Health “Pepper Oil Aroma Helps Elderly With Swallowing”
  • Ebihara 2006 J Am Geriatr Soc 54 p1401 “A Randomized Trial Of Olfactory Stimulation Using Black Pepper Oil In Older People With Swallowing Dysfunction”

One hundred five elderly Japanese who had trouble swallowing were randomly divided into three groups.  One group was exposed to black pepper oil (BPO), one to lavender, and one to distilled water.  There was a significant increase in the speed of swallowing reflex, concentration of serum substance P, and number of swallows per minute for the group exposed to BPO but not for the other groups.  Brain scans were taken for ten individuals in the black pepper oil group before and after treatment.  Inhalation of BPO apparently also activates two regions of the brain.  Since difficultly in swallowing is linked to difficultly in breathing, the authors argue that exposure to BPO may help prevent pneumonia in the elderly.

Suggested Lesson Structure:

  • Answer questions about and discuss the two articles
  • Activity: Design This Experiment

Discussion Points:

  • Have the students answer these questions in groups of 3 or 4.  They are expected to have already read the articles before coming to class:
    • What is the motivation for studying the effect black pepper scent on swallowing reflex?
    • What was the design of the experiment, in general terms?
    • How many subjects were in the experiment?
    • What is good evidence that they were randomly assigned to the three groups?
    • What different measurements were taken and why do you think they looked at so many?
    • What were the controls and why do you think they were chosen?
    • Why were the brainscans done and what do they show?
    • Was the main hypothesis proved in this experiment?

Active Learning Modules:

  • Design This Experiment
    • Divide students into groups of 3 or 4.
    • Give each group an hypothesis and tell them to design a reasonable experiment to test it.
    • Make sure they include: basic design, study flow, description of test subjects (human females between the ages of 6 and 10, male adult mice, etc), controls, use of randomness, double-blind, reasonable sample size, types of measurements.
    • Students do not need to say which statistical test or analysis they will use.
    • Examples of possible hypotheses:
      • Cell phones lower sperm count
      • Human females dress “flashier” while ovulating
      • Daily consumption of energy drinks leads to a deadly over-accumulation of B vitamins
      • Lack of sleep increases weight gain
      • Taller women are more likely to have twins due to an above normal amount of an insulin-like growth factor
      • Drinking cola leads to weaker bones in women
      • People with higher IQs are more likely to be vegetarians
      • Eating chocolate lowers chance of heart attacks
      • The act of spending 10 minutes each night contemplating three things that went well during the day makes people happier
      • Lack of vitamin D increases risk of getting the flu
      • Green tea prevents cancer
      • Caffeine acts as a diuretic
      • Taking gingko everyday improves memory

Note: These are all examples of published studies.

Additional Links:

Pepper oil aroma helps elderly with swallowing

A Randomized Trial of Olfactory Stimulation Using Black Pepper Oil in Older People with Swallowing Dysfunction