In a sample of 500 voters, 400 indicated they favor the incumbent governor. The 95% confidence interval of voters not favoring the incumbent is
A. 0.782 to 0.818
B. 0.120 to 0.280
C. 0.765 to 0.835
D. 0.165 to 0.235
A sample of 92 observations is taken from an infinite population. The sampling distribution of is approximately
A. normal because is always approximately normally distributed
B. normal because the sample size is small in comparison to the population size
C. normal because of the central limit theorem
D. None of these alternatives is correct.
Michael is running for president. The proportion of voters who favor Michael is 0.8. A simple random sample of 100 voters is taken. What is the probability that the number of voters in the sample who will not favor Michael will be between 26 and 30?
The sample size needed to provide a margin of error of 2 or less with a .95 probability when the population standard deviation equals 11 is
From a population that is not normally distributed and whose standard deviation is not known, a sample of 20 items is selected to develop an interval estimate for μ.
A. The normal distribution can be used.
B. The t distribution with 19 degrees of freedom must be used.
C. The t distribution with 20 degrees of freedom must be used.
D. The sample size must be increased.
using an = 0.04 a confidence interval for a population proportion is determined to be 0.65 to 0.75. If the level of significance is decreased, the interval for the population proportion
A. becomes narrower
B. becomes wider
C. does not change
D. remains the same
A department store has determined that 25% of all their sales are credit sales. A random sample of 75 sales is selected. What is the probability that the sample proportion will be greater than 0.34?
upper and lower control limits are usually based upon __________.
A. 3 standard deviations
B. 2 standard deviations
C. 1 standard deviation
D. 4 standard deviations
The probability distribution of all possible values of the sample mean is
A. the probability density function of
B. the sampling distribution of
C. the grand mean, since it considers all possible values of the sample mean
D. one, since it considers all possible values of the sample mean
A random sample of 121 checking accounts at a bank showed an average daily balance of $300 and a standard deviation of $44. Develop a 95% confidence interval estimate for the mean of the population.
A. $290.01 to $305.35
B. $288.21 to $301.01
C. $294.30 to $307.88
D. $292.16 to $307.84
A population has a mean of 300 and a standard deviation of 18. A sample of 144 observations will be taken. The probability that the sample mean will be between 297 to 303 is
In a poll of 600 voters in a campaign to eliminate non-returnable beverage containers, 210 of the voters were opposed. Develop a 92% confidence interval estimate for the proportion of all the voters who opposed the container control bill.
A. 0.300 to 0.360
B. 0.310 to 0.378
C. 0.332 to 0.412
D. 0.316 to 0.384
Nels Neugent, Purchasing Manager at Mid-West Medical Center, is designing a P chart to monitor the proportion of defective purchase orders issued at Mid-West. He has the proportions defective for 22 samples of purchase orders. Each sample contained 150 purchase orders, and the average proportion defective is 0.08. The centerline for Nels’ P chart is __________.
A random sample of 100 credit sales in a department store showed an average sale of $120.00. From past data, it is known that the standard deviation of the population is $40.00. Determine the standard error of the mean.
The purpose of statistical inference is to provide information about the
A. sample based upon information contained in the population
B. population based upon information contained in the sample
C. population based upon information contained in the population
D. mean of the sample based upon 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 if the desired margin of error is 5 or less is
The fact that the sampling distribution of sample means can be approximated by a normal probability distribution whenever the sample size is large is based on the
A. central limit theorem
B. fact that we have tables of areas for the normal distribution
C. assumption that the population has a normal distribution
D. None of these alternatives is correct.
A random sample of 121 bottles of cologne showed an average content of 4 ounces. It is known that the standard deviation of the contents (i.e., of the population) is 0.22 ounces. The point estimate of the mean content of the bottles is
A property of a point estimator that occurs whenever larger sample sizes tend to provide point estimates closer to the population parameter is known as
B. unbiased sampling
D. relative estimation
A department store has determined that 25% of all their sales are credit sales. A random sample of 75 sales is selected. What is the probability that the sample proportion will be less than 0.10?
A department store has determined that 25% of all their sales are credit sales. A random sample of 75 sales is selected. What is the probability that the sample proportion will be between 0.196 and 0.354?
A random sample of 150 people was taken from a very large population. Ninety of the people in the sample were female. The standard error of the proportion is
A population has a mean of 180 and a standard deviation of 24. A sample of 64 observations will be taken. The probability that the sample mean will be between 183 and 186 is
A local health center noted that in a sample of 400 patients 80 were referred to them by the local hospital. What size sample would be required to estimate the proportion of hospital referrals with a margin of error of 0.08 or less at 95% confidence?
Ten percent of the items produced by a machine are defective. A random sample of 100 items is selected and checked for defects. What is the probability that the sample will contain more than 2.5% defective units?