# Hypothesis Testing

STAT 20: Introduction to Probability and Statistics

## Agenda

• Announcements
• Concept Questions
• Problem Set 13: Hypothesis Tests? (first page)
• Break
• Problem Set 13: Hypothesis Tests? (second page)

# Concept Questions

Which of the following statements below represents claims that correspond to a null hypothesis (as opposed to an alternative hypothesis)?

Hint: try to write them using parameters (statements about means / proportions / etc)

A. King cheetahs on average run the same speed as standard spotted cheetahs.

B. For a particular student, the probability of correctly answering a 5-option multiple choice test is larger than 0.2 (i.e., better than guessing).

C. The mean length of African elephant tusks has changed over the last 100 years.

D. The risk of facial clefts is equal for babies born to mothers who take folic acid supplements compared with those from mothers who do not.

E. Mean birth weight of newborns is dependent on caffeine intake during pregnancy.

F. The probability of getting in a car accident is the same if using a cell phone than if not using a cell phone.

01:00

A pharmaceutical company developed a new treatment for eczema and performed a hypothesis test to see if it worked better than the company’s old treatment. The P-value for the test was $10\%$. Which one of the following statements are true?

A. The probability that the null hypothesis is false is $10\%$.

B. The P-value of about $10\%$ was computed assuming that the null hypothesis was true.

C. The new drug is significantly better than the old.

D. The alternative hypothesis is 10 times more likely the null.

01:00

# Problem Set 13

Is yawning contagious?

## What do you think?

Answer at pollev.com.

# Problem Set 13:

• Now, we will watch a short excerpt from a Mythbusters episode in which the Mythbusters crew sets up, performs and analyzes the results of an experiment designed to test whether yawning is contagious.

## What do you think about the of the experiment in the video?

• Discuss with your group, identifying anything that seems amiss.
01:30

# Problem Set 13: Page 1

20:00

# Break

05:00

# Problem Set 13: Page 2

20:00

## Do you still think yawning is contagious?

Answer at pollev.com.