Question

Suppose 80% of the incoming email messages for a college’s computer system are spam. 1. Use the CLT to approximate the probability that in a random sample of 200 incoming email messages at this college, the sample proportion of these messages that are spam would exceed .75. 2. Display your answer to question 1 as a shaded area in a well-labeled sketch. 3. After implementing a new spam blocker, if it turns out that a random sample of 200 messages contains 75% spam, would this constitute fairly convincing evidence that the (population) percentage of spam has been reduced from 80%?Explain, based on your calculation in question 1. 4. Would your answer to question 1 be larger, smaller, or the same if the sample size were 100 messages rather than 200 messages? Explain briefly. 5. Would your answer to question 1 be larger, smaller, or the same if the (population) proportion of spam messages were .77 rather than .80? Explain briefly.

Answer #1

According to MessageLabs Ltd., 80% of all email sent in July
2010 was spam. A system manager at a large corporation believes
that the percentage at his company may be greater than 80%, and he
wants to do a hypothesis test to see if there is evidence to
support his belief. He examines a random sample of 500 emails
received at an email server and finds that 420 of the messages are
spam.
What is the parameter for this hypothesis...

According to MessageLabs Ltd., 80% of all email sent in July
2010 was spam. A system manager at a large corporation believes
that the percentage at his company may be greater than 80%, and he
wants to do a hypothesis test to see if there is evidence to
support his belief. He examines a random sample of 500 emails
received at an email server and finds that 420 of the messages are
spam.
What is the parameter for this hypothesis...

QUESTION 7
Suppose the observational units in a study are the patients
arriving at an emergency room on a given day, 11 Nov 2019. For the
following indicate whether it can legitimately be considered a
variable or not:
Whether or not men have to wait longer than women
yes
no
5 points
QUESTION 8
A survey company published results of a survey stating that 56%
of the 600 randomly sampled residents planned to set off
firereworks on July...

1. i) Let's consider a hypothetical economy where this year's
money supply is Tk. 300, nominal GDP is Tk. 80000 and real GDP is
Tk. 2000. a) What does the quantity theory of money say? b)
Calculate the price level. c) Calculate the velocity of money d)
Show stage b on a graph. ii) Describe briefly the tools the central
bank uses to control the money supply in the economy, 3. a) Suppose
economists observe that an increase in government...

1. Do you check your phone or use technology right before you go
to bed? If so, chances are that you are not alone. A recent news
report claims that 60% of adults use some kind of technology right
before they go to bed at night. Believing that this claimed value
is too low, a researcher surveys a random sample of 200 adults and
finds that 71% use some kind of right before they go to bed. If a
hypothesis...

The vast majority of people have hand dominance--they are either
left-handed or right-handed.
In this question we will ignore the very small percentage of the
population who are
ambidextrous (i.e., those who use both hands equally well or
equally badly!).
A researcher believes that men are more likely to be left-handed
than women. To check this she
checked the dominant hand of random samples of 200 men and 200
women, and found 24 men
and 18 women to be left-handed....

Question 1:
The following bivariate data set contains an outlier.
x
y
51.7
82.9
51.3
75
52.5
71.4
52.5
74.2
43.6
66.6
37.1
81.8
52.8
63.4
58.4
59.8
61.7
49
35.9
79.9
62.7
76.6
43.4
69.3
35.5
86.9
50.6
57.3
144.3
200.6
What is the correlation coefficient with the
outlier?
rw =
What is the correlation coefficient without the
outlier?
rwo =
Would inclusion of the outlier change the evidence for or against a
significant linear correlation at 5% significance?...

1. When constructing a confidence interval to estimate a
population proportion, what affects the size of the margin of
error?
A. The sample size
B. The sample proportion
C. The confidence level
D. All of the above affect the size of the margin of error
E. None of the above affect the size of the margin of error
2. What percentage of couples meet through online dating
apps? A survey of a random sample of couples finds that 12% say...

1. Continuing from the questions on Homework 1, suppose the
following Earned Income Tax Credit (EITC) scheme is put in place.
For those whose earned income is less than $500 per week the
government gives 40 cents on every dollar earned. For those who
earn more than $500 the government gives them $200 per week. Based
on the answers to question 2 of the first homework (i.e. ignore
overtime), how does this affect the labor supply and earnings of
Johnny...

BridgeRock is a major manufacturer of tires in the U.S.. The
company had five manufacturing facilities where tires were made and
another 20 facilities for various components and materials used in
tires. Each manufacturing facility produced 10,000 tires every
hour. Quality had always been emphasized at BridgeRock, but lately
quality was a bigger issue because of recent fatal accidents
involving tires made by other manufacturers due to tread
separation. All tire manufacturers were under pressure to ensure
problems did not...

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