Chapter 8 LearnSmart

A t distribution A. has slightly broader tails than the z distribution B. does not have asymptotic tails C. is either positively skewed or negatively skewed D. has a nonzero mean

A. has slightly broader tails than the z distribution

When the sample size is sufficiently large, we can approximate the sampling distribution of the sample proportion using the A. exponential distribution B. uniform distribution C. normal distribution D. t sub df distribution

C. normal distribution

A confidence interval narrows if the following is accomplished: (choose 2 answers) A. the chosen confidence level increases B. the sample size decreases C. the chosen confidence level decreases D. the sample size increases

C. the chosen confidence level decreases D. the sample size increases

Which of the following is the correct formula for margin of error in the interval estimation of p? A. *sqrt* p(1-p)/n B. *sqrt* p hat(1-p hat)/n C. z sub alpha/2 *sqrt* p hat(1- p hat)/n D. t sub alpha/2,df *sqrt* p hat (1- p hat)/n

C. z sub alpha/2 *sqrt* p hat(1- p hat)/n

What is the value of z sub alpha/2 for a 90% confidence interval for the population mean? A. 1.96 B. 0.05 C. 0.10 D. 1.645

D. 1.645

When constructing a confidence interval for the population mean, the factors that affect the width of the confidence interval for a given standard deviation are A. the point estimate and the confidence level B. the confidence level, the sample size, and the point estimate C. the confidence level and the sample size D. the point estimate and the sample size

C. the confidence level and the sample size

Suppose you are constructing a confidence interval for the population mean. For a given sample size and standard deviation, the width of the confidence interval is _______ for a greater confidence level. A. the same B. narrower C. wider

C. wider

When examining the possible outcome of an election, what type of confidence interval is most suitable for estimating the current support for a candidate? A. confidence interval for the population proportion B. confidence interval for the sample mean C. confidence interval for the population mean D. confidence interval for the sample proportion

A. confidence interval for the population proportion

A sample of 25 is drawn from a normal population with a population standard deviation of 100. A sample mean of 35 is calculated. For a 95% confidence interval z *sub* 0.0025=1.96. A 95% confidence interval for the population mean is equal to: A. 35+/- 1.96 25/*sqrt*100 B. 35 +/- 1.96 100/*sqrt* 25 C. 25 +/ 1.96 100/*sqrt* 35 D. 25 +/- 1.96 35/*sqrt*100

B. 35 +/- 1.96 100/*sqrt* 25

A sample of 16 is drawn from a normal population with an unknown population standard deviation. The sample mean and the sample standard deviation is calculated as 50 and 25, respectively. For a 95% confidence interval z sub 0.025=1.96 and t sub 2.131. A 95% confidence interval for the population mean is equal to A. 25 +/- 2.131 50/*sqrt* 16 B. 50 +/- 2.131 25/*sqrt* 16 C. 50 +/- 1.96 25/*sqrt* 16 D. 25 +/- 1.96 50/*sqrt*16

B. 50 +/- 2.131 25/*sqrt* 16

A 95% confidence interval for the population mean is constructed as 6 +/- 2. What is the point estimate? A. 0.95 B. 0.05 C. 6 D. 2

C. 6

When estimating the population mean, the t sub df distribution is used when the A. size of the population is unknown B. population standard deviation is known C. population mean is unknown D. population variance is unknown

D. population variance is unknown

Suppose you are constructing a confidence interval for the population mean. For a given confidence level and sample size, the width of the interval is wider for a A. larger standard deviation B. smaller standard deviation C. smaller point estimate D. larger point estimate

A. larger standard deviation

Alpha is often referred to as the A. level of significance B. point estimate C. confidence coefficient D. margin of error

A. level of significance

In order to construct a confidence interval for mu, the sampling distribution of the estimator x bar must follow or approximately follow a(n)_____ distribution. A. normal B. binomial C. exponential D. uniform

A. normal

True or false: The t sub df distribution is a bell-shaped and symmetric around 0. A. true B. false

A. true

If alpha equal 0.05, the the confidence coefficient equal A. 0.975 B. 0.95 C. 0.05 D. 0.025

B. 0.95

Whenever we construct a confidence interval for the population mean, the margin of error includes the standard error of x bar and the A. sampling bias B. nonresponse bias C. z or t value associated with a 95% confidence level D. desired level of confidence

D. desired level of confidence

The parameter _______ represents the proportion of successes in a population and the statistic _______ represents the proportion successes in a sample. A. sigma, s B. mu, x bar C. s, sigma D. p, p bar

D. p, p bar

The estimator x bar follows a normal distribution when the underlying population follows a ___________ distribution

normal

The standard error of the sample mean is NOT affected by the A. standard deviation B. variance C. sample size D. confidence level

D. confidence level

(refer to question 24 photo) The following tables lists t sub df values for the selected upper-tail probabilities and degrees of freedom df. If df=6 and alpha=0.05, find t sub alpha/df. A. 2.447 B. 1.860 C. 1.943 D. 1.895

A. 2.447

How does an interval estimator differ from a point estimator? A. if a point estimator fails to produce an unbiased result, then an interval estimator secures such a result B. an interval estimator provides a range of values that always include the population parameter whereas a point estimator does not usually include it C. A point estimator may produce very biased results, while an interval estimator never has such a feature D. An interval estimator provides a range of values for the population parameter whereas a point estimator provides a single value

D. An interval estimator provides a range of values for the population parameter whereas a point estimator provides a single value

The two pieces of information that are necessary to determine the value of t sub df are A. the population standard deviation B. the level of significance C. the population mean D. the sample size or degrees of freedom

B. the level of significance D. the sample size or degrees of freedom

The confidence level is equal to A. 100 x (alpha/2) % B. 100 x alpha % C. 100 x (1-alpha)/2% D. 100 x (1-alpha) %

D. 100 x (1-alpha) %

Which of the following is description measure for a qualitative variable? A. standard deviation B. median C. mean D. proportion

D. proportion

For a 95% confidence interval in which the value of sigma is known, there is a 95% probability that the sample mean x bar will fall in the interval mu +/- ___________ x sigma/*sqrt*n A. 1.96 B. 1.645 C. 2.576 D. 1.28

A. 1.96