Confidence Intervals
What is at the center of a CI?
the point estimate
What is the formula for a one-sample hypothesis test for a mean?
on green sheet
What is Type I error?
Falsely rejecting a true null hypothesis
When should you run a one-sided test? When do you run a two-sided test?
One sided: alternative hypothesis is > or <
Two sided: alternative hypothesis is not equal to
What is Ali's favorite color
purple
What is the goal of creating a CI?
To estimate the Population Parameter
when the p-value is less than alpha
What is Type II error?
Falsely failing to reject a false null hypothesis
True or False:
The higher the level of confidence we want, the narrower our confidence interval becomes
False
What is Ali's major?
Psychology
Give me some keywords/things in a problem that tell you to run a Confidence Interval test?
- Confidence level (sometimes)
- Give an estimate
- Only given info about sample
Give me some keywords/things in a problem that tell you to run a hypothesis test?
- Evidence
- A direction (a research hypothesis)
- Information is given about the sample and the population
What tells us the probability of Type I error
alpha
Do we prove anything in this class?
NEVER
How many siblings does Ali have?
Three
two brothers one sister
Write a confidence statement: A researcher asked 330 random college students, and found that a 98% confidence interval for the mean hours per week spent studying is (13, 17).
Multiple answers
A statistics professor at a large university wants to know if more than 80% of her students enjoyed taking her classes. A p-value = 0.0235 was found when a HT was run.
Multiple right answers
What kind of relationship do alpha and beta have?
inverse: as alpha increases, beta decreases
What type of test should we run for this problem:
A random sample of 45 Hollywood movies made since year 2000 had a mean length of 111.7 minutes, with a SD of 13.8 minutes. Estimate the true mean length of all Hollywood movies since 2000.
CI for Mean
What is Ali's favorite hockey team?
Boston Bruins
Create a 95% CI, do all the steps of the problem:
A random sample of 45 Hollywood movies made since year 2000 had a mean length of 111.7 minutes, with a SD of 13.8 minutes. Estimate the true mean length of all Hollywood movies since 2000.
(107.6, 115.8)
Do all the steps of this problem:
An insurance company states that at least 90% of its claims are settled within 30 days. A consumer group selected a random sample of 190 of the company’s claims to test this statement. The consumer group found that 178 of these claims were settled within 30 days. Does the consumer group have sufficient reason to support the contention that at least 90% of the claims are settled within 30 days?
p-value: 0.0452
Reject H0
Describe Type I error in the context of this problem:
A statistics professor at a large university wants to know if more than 80% of her students enjoyed taking her classes. At the end of the term, she takes a random sample of students from her large classes and asks, in an anonymous survey, if the students enjoyed taking her class. Out of the 53 who were sampled, 44 enjoyed her class.
They find that more that 80% of the students enjoy the class when 80% or less enjoy the class.
What is the difference in the Success/Fail condition between CI and HT
In CI, we do the sample size times the sample proportion
In HT, we do the sample size times the population proportion
Where is Ali going to do her masters? (bonus points if you know what her masters is going to be in)
University of Illinois - Moral Development