An LA Times poll found that 52% of sample respondents preferred
cutting spending on social programs as opposed to raising taxes as a
way to reduce government expenditures
Find an approximate 95% CI for the proportion of adults who feel this
way if the sa
Lecture 20
Problem: The weight distribution of parcels is normal with mean value 12lb and std dev 3.5lb.
The parcel service wants to establish a weight c beyond which there is a surcharge. What is the
value of c such that 99% of parcels are at least 1lb u
Information for Midterm Exam 1 STAT 270
Last update: May 28th, 10:00am.
WHEN and WHERE.
The first midterm exam will be on Friday May 29th from 9:30am to 10:20am in our regular
classroom on Images Theatre.
PROCEDURES.
Please wait outside the classroom un
Information for Midterm Exam 2, STAT 270
Last update: June 17th, 4:30pm.
WHEN and WHERE.
The second midterm exam will be on Friday June 19th from 9:30am to 10:20am in our regular
classroom on Images Theatre.
PROCEDURES.
Please wait outside the classroom
A coin is ﬂipped until a head appears. What is the probability that a head appears on an odd—
numbered ﬂip? Simplify as much as possible and ShOW work (explaining where needed).
Owiwwes a} "mitt/Psi “14‘ H} Ti” \t) "TTTTllj i}
?V0\00\5\¥E§ Lineag “Q Q‘C’c
Information for Midterm Exam 3, STAT 270
Last update: June 8th, 5:00pm.
WHEN and WHERE.
The second midterm exam will be on Friday July 10 th from 9:30am to 10:20am in our regular
classroom on Images Theatre.
PROCEDURES.
Please wait outside the classroom
1; 4%
1. (Based on a problem from “Stats, data and models” by De Veaux et a1.) Does how long children
remain at the lunch table help predict how much they eat? The table gives data on 20 toddlers
observed over several months at a nursery school. “Time” i
l. A multiple choice exam has 50 questions. Each question has potential answers A, B, C, D, and
E. The instructor wants to give one mark for a correct answer, zero marks for a non-response
and x marks for an incorrect answer such that someone who guesses
1.
Consider X~binomial(1,1/3) independent of Y~binomial(2,1/2). Obtain the pmf of W = XY + 1.
X g 0 CU} f «*v M( \l 3/
\ w 13$ «7w Saab} \1 593 V13 keﬂkw
0
f0rw>0
2. Let the pdf for random variable W be f(w) = f (w) ={ > '
otherwzse.
E( W) Va» C W)
F ind
Information for Midterm Exam 4, STAT 270
Last update: July 29th, 11:30am.
WHEN and WHERE.
The fourth midterm exam will be on Friday July 31st from 9:30am to 10:20am in our regular
classroom on Images Theatre.
PROCEDURES.
Please wait outside the classroo
Problem: (Lecture 14, page1) A friend recently planned a camping trip. He had two
flashlights, one that required a single 6-V battery and another that used two size-D batteries. He
had previously packed two 6-V and four size-D batteries in his camper. Sup
Problem (FROM Lecture 11): A library subscribes to two weekly magazines, each of which is suppose to
arrive on Wednesdays. In actuality, the two magazines arrive independently with probabilities of arrival,
P(Wed) = 0.3, P(Thu) = 0.4, P(Fri) = 0.2 and P(S
Examples of parameters:
Population mean ( eg. Average age of people in the population)
Population proportion (eg. Proportion of people who support
tuition increases)
Examples of statistics:
Sample mean
Sample proportion
A 95% confidence interval is an in
Observations
Sharper curve = smaller standard deviation
Bigger curve = larger standard deviation
Suppose have a sample of size n from a
distribution
A level C confidence interval is:
[ xBar-Z (sigma/ sqrt n), xBar+Z (sigma/ sqrt n) ]
Xbar = number calcul
Earlier, we concerned ourselves with numerical/graphical summaries
of samples (x1, x2, , xn) from some population
Can view each of the Xis as random variables
We will be concerned with random samples
The Xis are independent
The Xis come from the same pop
Suppose that r2=.81. What does this mean?
Implies that 81% of the observed variation in the GPA scores is
explained by the linear relationship with IQ
What is the correlation?
Correlation is r=0.90 How do we know it is not -0.90?
Must have same sign as t
NCAA Division II requires that athletes get a combined score of at
least 820 on the SAT exam in order to compete in their first year of
college sports. SAT scores for college-bound students are normally
distributed with a mean of 1012 and standard deviat
Recall that probabilities must lie between 0 and 1
Represent the long term proportion of ties an outcome is observed
based on repeated samples
Use P( ) as shorthand for The probability of ( ),where inside the ( )
you name some event.
Roll a die. What is
A coin is tossed 2 times
S= cfw_ (H,T), (T,H), (H,H), (T,T)
What is the probability of getting not getting a tails?
Two solutions:
1.
A= (H,H) P(A) =
2.
A^C = (H,H), (T,H), (T,T)
P(A) = 1-P(A^C) = 1-3/4 = 1/4
Example: All outcomes of rolling 2 dice:
(1
Suppose have 1000 people in a population (500 male and 500
female) and average age of the males is 26 and average age of
females is 24
What is the mean age in the population?
25 years old
Suppose have 1000 people in a population (900 male and 100
female)
In most real problems, models are based on
. Combinations of
Data
Theory
Assumptions
This is the most common way to form models
Uses whatever knowledge is available
Fills in missing parts with assumptions
Probability of event, A is denoted P(A)
S = sampl
Information for Final Exam, STAT 270
Last update: August 11th, 12:30pm.
WHEN and WHERE.
The Final Exam will be on Thursday August 13th from 3:30pm to 6:30pm in our regular
classroom on Images Theatre.
PROCEDURES.
Please wait outside the classroom until