Download Topic 19 Concept Check

Confidence Interval Concept
Check
A laboratory scale is known to have a standard deviation of 0.001 gram in repeated
weighings. Scale readings in repeated weighings are Normally distributed, with mean
equal to the true weight of the specimen. If you weigh a specimen three times on this
scale, the mean result has standard deviation of …
a.
b.
c.
d.
0.001 gram
0.000577 gram
0.000333 gram
a, b, and c are all
incorrect
62%
29%
10%
0%
a.
b.
c.
d.
Three weighings of a specimen on the scale described previously (Normal
with σ = 0.001) give 3.412 grams, 3.416 grams, and 3.414 grams. What is a
95% confidence interval for the true mean weight?
a. (3.4129, 3.4151)
b. (3.4134, 3.4147)
c. (3.409, 3.419)
86%
5%
a.
b.
10%
c.
Another specimen is weighed 8 times on the same scale (N, σ = 0.001).
The average weight is 4.1602 grams. What is a 99% confidence
interval for the true mean weight of this specimen?
90%
a. (4.15988, 4.16052)
b. (4.15951, 4.16089)
c. (4.15929, 4.16111)
10%
0%
a.
b.
c.
Same scale (N, σ = 0.001)…How many times must you weigh a
specimen in order to get a margin of error no larger than +/0.0005 with 95% confidence?
90%
a.
b.
c.
d.
4 times
5 times
15 times
16 times
0%
a.
5%
b.
5%
c.
d.
An opinion poll says that the result of their latest sample has a margin
of error of plus or minus three percentage points, with 95%
confidence. This means that…
a.
b.
c.
We can be certain that the poll
result is within three percentage
points of the truth about the
population.
We could be certain that the poll
result is within three percentage
points of the truth if there were
no nonresponse.
The poll used a method that
gives a result within three
percentage points of the truth in
95% of all samples.
90%
5%
a.
5%
b.
c.
A government report says that a 90% confidence interval for the mean
income of American households is $59,067 +/- $356. This is based on a
random sample of 60,000 households. If the same sample results had come
from a sample of 15,000 households, the new margin of error would be…
a.
b.
c.
d.
+/- $712
+/- $356
+/- $178
a, b, and c are all
incorrect
90%
0%
a.
b.
5%
c.
5%
d.
Suppose that the survey in the previous problem (MOE = $356) had obtained the
sample mean $59,067 from a sample of 60,000 households in Ohio (population 11.5
million) instead of from all households in the United States (population 300 million).
The margin of error for 90% confidence would be …
95%
a. About +/- $356
b. Greater than +/$356
c. Less than +/- $356
0%
a.
b.
5%
c.
Same report (MOE=$356 with 90% confidence)…Suppose the
report had used 95% confidence rather than 90% confidence.
The margin of error would be…
95%
a. +/- $356
b. Greater than +/$356
c. Less than +/- $356
5%
0%
a.
b.
c.
Data on the blood cholesterol levels of 6 rats (milligrams per
deciliter of blood) give a sample mean of 85 and a sample
standard deviation of 12. A 95% confidence interval for the
mean blood cholesterol of rats under this condition is…
76%
a. (72.4, 97.6)
b. (73.0, 97.0)
c. (75.4, 94.6)
24%
0%
a.
b.
c.
We prefer the t procedures to the z procedures for
inference about a population mean because…
100%
a. Z can be used only for
large samples
b. Z requires that you
know the population
standard deviation
c. Z requires that you can
regard your data as an
SRS from the
population
0%
a.
0%
b.
c.
You have an SRS of 15 observations from a Normally distributed
population with s = 1.765. What critical value would you use to
obtain a 98% confidence interval for a population mean?
a.
b.
c.
d.
2.326
2.602
2.624
a, b, and c are all
incorrect
67%
29%
5%
0%
a.
b.
c.
d.
Which of the following math terms is
correctly spelled?
a.
b.
c.
d.
e.
f.
g.
h.
Pythagorean
Isocseles
Supplimentary
Statisticaly
Empiracal Rule
Test of Significants
Criticle Value
Parrabola
13%
13%
a.
b.
13%
13%
13%
c.
d.
e.
13%
f.
13%
13%
g.
h.