"A machine that produces metal rods used in an automobile suspension system is being tested to
make sure that the average diameter of rods it produces does not exceed 8.20mm. A random
sample of 15 rods is selected, and the diameter (in mm) is measured for

Glossary for exam 3
: The symbol for level of significance.
: The probability of failing to reject a false null hypothesis.
Alternative hypothesis : The hypothesis that the researcher wants to prove or verify; a statement about the value
of a parameter th

Lecture Review for Exam 3 Overheads
1. Using 16 measurements (in millimeters) of a critical dimension on a
random sample of auto engine crankshafts from a Normally distributed
population, we obtained the following 95% confidence interval estimate
for : (2

Lecture Review for Exam 3 with answers
1. Using16 measurements (in millimeters) of a critical dimension on a random sample of auto engine
crankshafts from a Normally distributed population, we obtained the following 95% confidence
interval estimate for :

Practice questions for Exam 3
1. Fill in the blank: The t-distribution with 8 degrees of freedom has _ the
standard Normal distribution.
A. the same center but is more spread out than
B. the same center but is less spread out than
C. the same center and s

Exam 3 Lecture Review
Statistics 221
1. A certain brand of fishing line claims to have an average
breaking strength of 30 pounds. A group of fishermen
become angry because this brand of line seems to break
so easily and test 25 randomly selected lines of

Study Guide for Exam 3
Be able to define
P-value
= level of significance
margin of error
type I error
type II error
confidence interval
confidence level
robustness of a statistical procedure
practical significance
statistical significance
Be able to inte

Jeopardy questions for exam 3
Confidence Intervals
1. The change in the width of a confidence interval when the sample size is increased
2. The change in the width of a confidence interval when the level of confidence is increased
3. With 90% confidence,

Realistic Inference about
a Population Mean
Student:
ordinary
guy who
changed
changed
the world
100
years
ago
Unrealistic Case
sampling dist. of x normal because
known
population normal, or n large enough
that central limit theorem makes
sampling distrib