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Stat 104
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Terms in this set (21)
T or F: The center of a 95% confidence interval for the population mean is a random variable
True
T or F: For the following situation, can the normal distribution be used to compute the answer?
Weights of adults have mean 150 lbs and standard deviation 25 lbs. We want to know
the probability that the average weight of 50 randomly selected people is more than
200 pounds
True
T or F: For the following situation, can the normal distribution be used to compute the answer?
Salaries at a large corporation have mean of $40,000 and standard deviation of $20,000.
We want to know the probability that a randomly selected employee makes more than
$50,000.
False
Sample 1, sample 2, or both are equal: Random samples are taken from two different populations. A sample of size 𝑛1 is taken
from population 1, which has a population standard deviation of
sd1
. A sample of size
𝑛2 = 2𝑛1 is taken from population two, which has a population standard deviation of
2sd1
. In which of the two samples would you expect the estimate of the population
mean to be more accurate?
Sample 1
The owner of a hotdog stand claims that the mean attendance at Trump rallies is over
72,100, and she is therefore justified in enlarging her stand before the next rally. Identify
the type II error for the test.
b) Fail to reject the claim that the mean attendance is equal to 72,100, when it is
actually over 72,100.
b
An unbiased estimator of a population parameter is defined as:
a) An estimator whose expected value is equal to the parameter
a
Which of the following statements is (are) true about the t-distribution with k degrees of
freedom?
i. The t-distribution is symmetric.
ii. The t-distribution with k degrees of freedom has a smaller variance than the t-distribution
with k+1 degrees of freedom.
iii. The t-distribution has a larger variance than the standard normal (z) distribution
1) I only
2) II only
3) III only
4) I and II
5) I and III
5 or E
A music producer is interested in marketing a new artist via ads in movie theaters. The
target age group is teenagers from 14-18 years of age. The company developing the
advertisement has offered to run the ad in conjunction with the following types of
movies: 20% of the time with comedies, 50% with dramas, and 30% with action films.Compute the
value of the Chi-square goodness of fit statistic.
Observed - Comedy:41, Drama:35, Action:24
e) 27.75
e
In a recent Gallup poll on a random sample of 1,028 US adults, 11% said they approve of
the way the Congress is handling its job, with a 95% confidence interval of 7% to 15%.
Which of the following statements is/are true based on the confidence interval?
(i) The population proportion is 0.11.
(ii) The sample proportion is 0.11.
(iii) The margin of error is 0.04.
(iv) 95% of random samples will have sample means between 0.07 and 0.15.
a) They all are true
b) None of them are true
c) (i), (iii) and (iv) are true
d) (ii) and (iv) are true
e) (ii) and (iii) are true
e
If a population is known to be normally distributed, then it follows that the sample
standard deviation must equal the population standard deviation for any size
sample.
b false
All t distributions have a mean of zero and a standard deviation of 1.
b false
If a 95% confidence interval for the mean number of hours that students study per
week is (18, 23), then there is a 95% chance that a randomly selected student will
study between 18 to 23 hours per week.
b false
A student wishes to know if SUV drivers at his school are more likely to be male
than female. He takes a simple random sample of 60 students from a large list of
students that consists of all the SUV drivers at the school, and records the gender
of each student in the sample. What would be the appropriate inference procedure
to use?
c) Test for a population proportion; testing to see if the proportion of
SUV drivers who are males is greater than 50%
c
Which of the following is a required condition for ANOVA?
a) The populations are not normally distributed.
b) The population variances are equal.
c) The samples are dependent.
d) All of these choices are not required conditions for ANOVA
b
A controversy that Americans have debated in recent years is the issue of gay
marriage. In a random sample of 180 American men, 90 of them claimed to have
supported gay marriage. In an independent random sample of 200 American
women, 150 claim to support gay marriage. Assume we are interested in the
proportion of men and women who support gay marriage. Which of the following
represents a pooled estimate for the proportion of all Americans who support gay
marriage under the null assumption of no difference?
a) 0.63
a
a
a
Suppose that 58% of all gold dealers believe next year will be a good one to
speculate in South African gold coins. In a simple random sample of 150 dealers,
what is the probability that between 55% and 60% believe that it will be a good
year to speculate?
0.46
A company claims that lifetime of the lightbulb they manufacture is normally
distributed with a mean of 240 hours and a standard deviation of 20 hours. An
assistant at the company makes an improvement to the lightbulb and claims that
the lifetime of the newer bulbs is normally distributed with a mean of 280 hours
and a standard deviation of 20 hours. If we let X represent the lifetime of the
lightbulb, this leads to the following null and alternative hypotheses.
Ho: X is N(240; 20)
Ha: X is N(280; 20)
Suppose the decision rule is that the null hypothesis will be rejected if the lifetime
of the lightbulb is greater than 280 hours. Determine the probability of a Type I
error.
a) 0.067
b) 0.023
c) 0.084
d) 0.075
e) 0.097
b
...
...
In conducting a chi-square test of association between gender and grade, what is
the expected count for the number of males who earned a grade of B?
73*69/141 (Total # of B's: 32+41=73 Total # of males: 10+32+25+2 = 69 Total in table: 10+5+32+41+25+14+2+12= 141 )
In conducting a chi-square test of association between gender and grade, what is
the expected count for the number of males who earned a grade of B?
73*69/141
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