Statistics Chapter 9 Exam Questions and Answers Latest Update 2024 Already Passed
A study of all the students at a small college showed a mean age of 20.9 and a standard deviation of 2.9
years.
Are these numbers statistics or parameters? Explain. - Answers The numbers are parameters because
they are for all the students, not a sample.
A study of all the students at a small college showed a mean age of 20.9 and a standard deviation of 2.9
years.
Label both numbers with their appropriate symbol (such as x bar, μ, s, or σ). - Answers μ=20.9
σ=2.9
A survey of 100 random full-time students at a large university showed the mean number of semester
units that students were enrolled in was 12 with a standard deviation of 1.9 units.
Are these numbers statistics or parameters? Explain. - Answers The numbers are statistics because they
are for a sample of students, not all students.
A survey of 100 random full-time students at a large university showed the mean number of semester
units that students were enrolled in was 12 with a standard deviation of 1.9 units.
Label both numbers with their appropriate symbol (such as x bar, μ, s, or σ). - Answers x bar=12
s=1.9
A biologist is studying the effects that applying insecticide to a fruit farm has on the local bat population.
She collects 23 bats and finds the mean weight of this sample to be 503.4 grams. Assuming the selected
bats are a random sample, she concludes that because the sample mean is an unbiased estimator of the
population mean, the mean weight of bats in the population is also 503.4 grams. Explain why this is an
incorrect interpretation of an unbiased estimator. - Answers Having an "unbiased" estimator means that
the mean of the means of all possible samples of the same size would be the same as the population
mean.
Several times during the year, an organization takes random samples from the population. One such
survey, based on a large (several thousand) sample of randomly selected households, estimates the
mean retirement income to be $21,201 per year. Suppose we were to make a histogram of all of the
, retirement incomes from this sample. Would the histogram be a display of the population distribution,
the distribution of a sample, or the sampling distribution of means? - Answers The histogram would be a
display of the distribution of a sample.
A human resources manager for a large company takes a random sample of 50 employees from the
company database. She calculates the mean time that they have been employed. She records this value
and then repeats the process: She takes another random sample of 50 names and calculates the mean
employment time. After she has done this 1000 times, she makes a histogram of the mean employment
times. Is this histogram a display of the population distribution, the distribution of a sample, or the
sampling distribution of means? - Answers The histogram is a display of the sampling distribution of
means.
The average income in a state was $56,000 per person per year. Suppose the standard deviation is
$29,000 and the distribution is right-skewed. Suppose we take a random sample of 100 residents of the
state.
What value should we expect for the sample mean? Why? - Answers The expected sample mean is
$56000, because the sample mean is an unbiased estimator of the population mean.
The average income in a state was $56,000 per person per year. Suppose the standard deviation is
$29,000 and the distribution is right-skewed. Suppose we take a random sample of 100 residents of the
state.
What is the standard error for the sample mean? - Answers The standard error for the sample mean is
$2900.
The average income in a state was $43,000 per person per year. Suppose the standard deviation is
$31,000 and the distribution is right-skewed. Suppose we take a random sample of 100 residents of the
state.
What value should we expect for the sample mean? Why? - Answers The expected sample mean is
$43000, because the sample mean is an unbiased estimator of the population mean.
The average income in a state was $43,000 per person per year. Suppose the standard deviation is
$31,000 and the distribution is right-skewed. Suppose we take a random sample of 100 residents of the
state.
A study of all the students at a small college showed a mean age of 20.9 and a standard deviation of 2.9
years.
Are these numbers statistics or parameters? Explain. - Answers The numbers are parameters because
they are for all the students, not a sample.
A study of all the students at a small college showed a mean age of 20.9 and a standard deviation of 2.9
years.
Label both numbers with their appropriate symbol (such as x bar, μ, s, or σ). - Answers μ=20.9
σ=2.9
A survey of 100 random full-time students at a large university showed the mean number of semester
units that students were enrolled in was 12 with a standard deviation of 1.9 units.
Are these numbers statistics or parameters? Explain. - Answers The numbers are statistics because they
are for a sample of students, not all students.
A survey of 100 random full-time students at a large university showed the mean number of semester
units that students were enrolled in was 12 with a standard deviation of 1.9 units.
Label both numbers with their appropriate symbol (such as x bar, μ, s, or σ). - Answers x bar=12
s=1.9
A biologist is studying the effects that applying insecticide to a fruit farm has on the local bat population.
She collects 23 bats and finds the mean weight of this sample to be 503.4 grams. Assuming the selected
bats are a random sample, she concludes that because the sample mean is an unbiased estimator of the
population mean, the mean weight of bats in the population is also 503.4 grams. Explain why this is an
incorrect interpretation of an unbiased estimator. - Answers Having an "unbiased" estimator means that
the mean of the means of all possible samples of the same size would be the same as the population
mean.
Several times during the year, an organization takes random samples from the population. One such
survey, based on a large (several thousand) sample of randomly selected households, estimates the
mean retirement income to be $21,201 per year. Suppose we were to make a histogram of all of the
, retirement incomes from this sample. Would the histogram be a display of the population distribution,
the distribution of a sample, or the sampling distribution of means? - Answers The histogram would be a
display of the distribution of a sample.
A human resources manager for a large company takes a random sample of 50 employees from the
company database. She calculates the mean time that they have been employed. She records this value
and then repeats the process: She takes another random sample of 50 names and calculates the mean
employment time. After she has done this 1000 times, she makes a histogram of the mean employment
times. Is this histogram a display of the population distribution, the distribution of a sample, or the
sampling distribution of means? - Answers The histogram is a display of the sampling distribution of
means.
The average income in a state was $56,000 per person per year. Suppose the standard deviation is
$29,000 and the distribution is right-skewed. Suppose we take a random sample of 100 residents of the
state.
What value should we expect for the sample mean? Why? - Answers The expected sample mean is
$56000, because the sample mean is an unbiased estimator of the population mean.
The average income in a state was $56,000 per person per year. Suppose the standard deviation is
$29,000 and the distribution is right-skewed. Suppose we take a random sample of 100 residents of the
state.
What is the standard error for the sample mean? - Answers The standard error for the sample mean is
$2900.
The average income in a state was $43,000 per person per year. Suppose the standard deviation is
$31,000 and the distribution is right-skewed. Suppose we take a random sample of 100 residents of the
state.
What value should we expect for the sample mean? Why? - Answers The expected sample mean is
$43000, because the sample mean is an unbiased estimator of the population mean.
The average income in a state was $43,000 per person per year. Suppose the standard deviation is
$31,000 and the distribution is right-skewed. Suppose we take a random sample of 100 residents of the
state.
