Statistics- A statement that is the sum of the products of the values

Question 16 4.3 pts

A statement that is the sum of the
products of the values of a random variable with its probability is

	the expected value.
	the variation of the random variable.

	an experiment.
	a probability distribution.

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Question 17 4.3 pts

In order to measure the dispersion
of a random variable, look at its

	standard deviation.
	mean

	expected value.
	average.

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Question 18 4.3 pts

The uniform distribution defined
over the interval from 20 to 40 has the probability density function

	f(x) = 1/40 for all x
	f(x) = 1/2 for 20 ≤ x ≤ 40 and f(x) = 0 elsewhere

	f(x) = 1/20 for 0 ≤ x ≤ 20 and f(x) = 1/40 for 21 ≤ x ≤ 40
	f(x) = 1/20 for 20 ≤ x ≤ 40 and f(x) = 0 elsewhere

Question
19 4.3 pts

If x is normally distributed with
mean 12 and standard deviation 2, then P(x ≤ 15) is

	P(z ≤ 5/4).
	P(z ≤ -3/2)

	P(z ≤ 3/2)
	P(z ≤ -5/4)

Question
20 12.9 ptsSkip to question text.

The high school GPAs of applicants
for admission to a college program are recorded and relative frequencies are
calculated for the categories.

GPA	f(x)
x < 2.0	.12
2.0 ≤ x < 2.5	.35
2.5 ≤ x < 3.0	.30
3.0 ≤ x < 3.5	.10
3.5 ≤ x

1. Complete the table to make this
   a valid probability distribution.
2. What is the probability an
   applicant’s GPA will be below 3.0?
3. What is the probability an
   applicant’s GPA will be 2.5 or above?

Question 21 17.35 ptsSkip to question text.

An instructor allows students to
take an exam as many times as needed until the student obtains a passing grade.
The following is a record of the number of students in a class of 20 who took
the test and the number of tests taken in order to obtain a passing grade.

Students	Number of Tests
9	1
6	2
3	3
2	4

1. Use the relative frequency
   approach to construct a probability distribution and show that it
   satisfies the required condition.
2. Find the expected value of the
   number of tests taken.
3. Compute the variance.
4. Compute the standard deviation.

Question
22 17.35 ptsSkip to question text.

A video rental store has two video
cameras available for customers to rent. Historically, demand for cameras has
followed this distribution. The revenue per rental is $40. If a customer wants
a camera and none is available, the store gives a $15 coupon for tape rental.

Demand	Relative Frequency	Revenue	Cost
0	.20	0	0
1	.10	40	0
2	.05	80	0
3	.35	80	15
4	.30	80	30

1. What is the expected demand?
2. What is the expected revenue?
3. What is the expected cost?
4. What is the expected profit?

Question 23 17.35 ptsSkip to question text.

The weight of a .5 cubic yard bag of
landscape mulch is uniformly distributed over the interval from 38.5 to 41.5
pounds.

1. Give a mathematical expression
   for the probability density function.
2. What is the probability that a
   bag will weigh more than 40 pounds?
3. What is the probability that a
   bag will weigh less than 39 pounds?
4. What is the probability that a
   bag will weigh between 39 and 40 pounds?

Question 24 4.3 pts

Time series methods do not include

	smoothing
	trend projections

	trend projection adjusted for seasonlity
	regression analysis

all of these are trend series methods

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Question 25 4.3 pts

A regular pattern recurring over
one-year (or shorter) periods is called

	seasonality
	cyclical component

	regression
	trend

Question
26 4.3 pts

To select a value for α for
exponential smoothing

	use a large α when the series varies substantially.
	use a small α when the series has little random variability.

	use any value
	All of the alternatives are true.

none of the alternatives are true

Question
27 4.3 pts

Causal models

	should avoid the use of regression analysis.
	attempt to explain a time series’ behavior.

	do not use time series data.
	All of the alternatives are true.

Question
28 4.3 pts

The number of cans of soft drinks
sold in a machine each week is recorded below. Develop forecasts using a three
period moving average.

328, 191, 187, 156, 241, 232, 198,
195, 178, 220

Question 29 4.3 ptsSkip to question text.

The number of girls who attend a
summer basketball camp has been recorded for the seven years the camp has been
offered. Use exponential smoothing with a smoothing constant of .8 to forecast
attendance for the eighth year.

57, 78, 75, 102, 108, 131, 164

Question 30 4.3 pts

A trend line for the attendance at a
restaurant’s Sunday brunch is given by
Number = 246 + .27(t)

How many guests would you expect in
week 30?