Quiz 5 Flashcards
(30 cards)
At 95% confidence interval for a population mean is detemined to be 100 to 120. If the confidence coefficent is reduced to 0.90, the interval for u (mew)
a. becomes 0.1
b. becomes wider
c. does not change
d. becomes narrower
Becomes NARROWER
A bank manager wishes to estimate the average waiting time for customers in line for tellers. A random sample of 50 times is measured and the average waiting time is 5.7 minutes. The population standard deviation of waiting time is 2 minutes. Which Excel function would be used to construct a confidence interval estimate?
a. CONFIDENCE.NORM
b. NORM.INV
c. INT
d. T.INV
CONFIDENCE.NORM
A manufacturer wants to estiamte the porportion of fedective items that are produced by a certain machine. A random smaple of 50 items are taken. Which Excel function would NOT be appropriate to construct a confidence interval estimate?
a. All are appropiate
b. NORM.S.INV
c. STDEV
d. COUNTIF
STDEV
A newspaper wants to estimate the proportion of Americans who will vote for Candidate A. A random sample of 1000 voters is taken. Of the 1000 respondants, 526 say that they will vote for Candidate A. Which Excel function would be used to construct a confidence interval estimate?
a. NORM.INV
b. NORM.S.INV
c. INT
d. T.INV
NORM.S.INV
A random sample of 25 employees of a local company has been measured. A 95% confidence interval estimate of the mean systolic blood pressure for all company employees is 123 to 139. Which of the following statements is valid?
a. 95% of the sample of employees has a systolic blood pressure btwen 123 and 139
b. If the sampling procedure were repeated many times, 95% of the resulting confidence intervals would contain the population mean systolic blood pressue
c. 95% of the population of employees has a systolic blood pressure between 123 and 139
d. If teh sampling prodecure were repeated many times, 95% of a sample means would be between 123 and 139
If the sampling procedure were repeated many times, 95% of the resulting confidence intervals would contain the population mean systolic blood pressure
A random sample of 36 students at a community college showed an average age of 25 years. Assume the ages of all students at the college are normall distributed with a standard deviation of 1.8 years. The 98% confidence interval for the average age of all students at this college is
a. 23.200 to 25.800
b. 24.301 to 25.699
c. 23.236 to 26.764
d. 24.385 to 25.615
24.301 to 25.6999
A sample of 26 elements from a normally distributed population is selected. The sample man is 10 with a standard deviation of 4. The 95% confidence interval for u is
a. 8.462 to 11.538
b. 8.384 to 11.616
c. 9.846 to 10.154
d. 6.000 to 14.000
8.384 to 11.616
An auto manufacturer wants to estimate the annual income of owners of a particular model of automobile. A random sample of 200 current owners is taken. The population standard deviation is known. Which Excel function would NOT be appropriate to use to construct a confidence interval estimate?
a. COUNTIF
b. AVERAGE
c. NORM.S.INV
d. STDEV
COUNTIF
An estimate of population parameter that provides an interval believed to contain the value of the parameter is known as the
a. parameter value
b. confidence level
c. population estiamte
d. interval estimate
Interval Estimate
In order to estimate the average time spent on the computer terminals per student at a local university, data were collected from a sample of 81business students over a one-week period. Assume the population standard deviation is 1.2 hours.
The standard error of the mean is
a. 0.160
b. 7.5
c. 0.014
d. 0.133
0.133
In order to estimate the average time spent on the computer terminals per student at a local university, data were collected from a sample of 81 business students over a one-week period. Assume the popuation standard deviation is 1.2 hours.
If the sample mean is 9 hours, then the 95% confidence itnerval is approximately
a. 7.04 to 110.96
b. 7.80 to 10.20
c. 7.36 to 10.64
d. 8.74 to 9.26
8.74 to 9.26 hours
A random sample of 81 automobiles traveling on a section of an interstate showed an avereage speef of 60 mph. THe distribtuion of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph.
The 86.9% confidence interval for u is
a. 57.735 to 62.265
b. 50 to 70
c. 59.131 to 60.869
d. 46.500 to 73.500
A. 57.735 to 62.265
A random sample of 81 automobiles traveling on a section of an interstate showed an avereage speef of 60 mph. THe distribtuion of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph
If we are interested in determining an interval estimate for u at 86.9% confidence, the z value to use is
a. 2.00
b. 1.51
c. 1.31
d. 1.96
1.51
For the interval esitmation of u when o is assumed known, the proper distribution to use is the
a. t distribution with n degrees of freedom
b. standard normal distribution
c. t distribution with n-1 degrees of freedom
d. t distribution with n-2 degrees of freedom
standard normal distribution
From a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for u. Which of the following statements is true?
a. the t distribution with 49 degrees of freedom must be used
b. the t disitribtuion with 50 degrees of freedom must be used
c. the sample size must be increased in roder to develop an interval estimate
d. The standard normal distribution can be used
The t distribution with 49 degrees of freefom must be used
If an interval estimate is said to be constructed at the 90% confidence level, the confidence coefficient would be
a. 0.05
b. 0.95
c. 0.9
d. 0.1
0.9
If we change a 95% confidence interval estimate to a 99% confidence interval, we can expect the
a. width of the confidence interval to remain the same
b. width of the confidence interval to decrease
c. sample size to increase
d. width of the confidence interval to increase
Width of the confidence interval to increase
In determining an interval estimate of a population mean when o is unknown, we use a t distribution with
a. 0 degrees of freedom
b. n degrees of freedom
c. n-1 degrees of freedom
d. n+1 degrees of freedom
n - 1 degrees of freedom
In determining the sample size neccessart to estimate a population proportion, which of the following information is NOT needed?
a. the mean of the population
b. the maximum margin of error that can be tolerated
c. a preliminary estimate of the true population proportion p
d. the confidence level required
The mean of the population
It is known that the population variance equals 484. With a 0.95 probability, the sample size that needs to be taken to estimate the population mean if the desired margin of error is 5 or less is
a. 75
b. 189
c. 25
d. 74
75
It is known that the variance of a population equals 1,926. A random sample of 121 has been taken from the population. There is a .95 probability that the sample mean will provide a margin or error of
a. 7.84 or less
b. 31.36 or less
c. 1,936 or less
d. 344.96 or less
7.84 or less
The confidence associated with an interval estimate is called the
a. degree of association
b. level of significance
c. precision
d. confidence level
Confidence level
The mean of the t distribution is
a. 0
b. 0.5
c. problem specific
d. 1
0
The t distribution is a family of similar probability distributions, with each individual distribution depending on a parameter known as the
a. finite correction factor
b. degrees of freedon
c. standard deviation
d. sample size
Degrees of Freedom
