As degrees of freedom increase, the t-distribution approaches the
binomial distribution.
exponential distribution
standard normal distribution
None of the above.
Given a t-distribution with 14 degrees of freedom, the area left of - 1.761 is
0.025
0.05
0.10
0.90
None of the above
100 samples of size fifty were taken from a population with population mean 72. The sample mean and sample standard deviation were recorded and the 95% confidence interval for the population mean was recorded for each sample. Of the 100 confidence intervals, how many would we expect to have 72 between the endpoints?
0
5
95
100
You are given a confidence interval for the population mean of 26 to 42. The sample mean used the construct this confidence interval was
1.96
26
34
Cannot be determined with the given information.
A sample of five price/earnings ratios for companies in the Services sector follows. 15 11 14 17 12 A confidence interval for the population mean is requested. In order to construct the confidence interval one must assume
that the sample came from a normal distribution.
that the population standard deviation is known.
No assumptions are needed.
None of the choices are correct.
A sample of five price/earnings ratios for companies in the Services sector follows. 15 11 14 17 12 A confidence interval for the population mean is requested. Assuming that the sample comes from a normal population, the appropriate distribution used in constructing this confidence interval is the
F
t
z
χ2
None of the choices are correct
A sample of five price/earnings ratios for companies in the Services sector follows. 15 11 14 17 12 A confidence interval for the population mean is requested. Assuming that the sample comes from a normal population, the appropriate degrees of freedom used for this confidence interval is
2
3
4
5
None of the choices are correct
A sample of five price/earnings ratios for companies in the Services sector follows. 15 11 14 17 12 A confidence interval for the population mean is requested. Assuming that the sample comes from a normal population, the appropriate degrees of freedom used for this confidence interval is
6.39 to 21.21
9.77 to 26.63
10.84 to 16.76
11.71 to 15.89
None of the choices are correct
A sample of five price/earnings ratios for companies in the Services sector follows. 15 11 14 17 12 A confidence interval for the population mean is requested. For the researcher's purpose, this interval is too wide. To make the interval more precise, the researcher should
decrease the sample size.
increase the sample size.
A sample of size 36 is taken from a population with standard deviation 12. The sample mean is found to be 116. In order to construct a confidence interval, one must assume that the population was normally distributed.
True
False
. A sample of size 36 is taken from a population with standard deviation 12. The sample mean is found to be 116. Construct a 95% confidence interval.
-25.89 to 49.89
95.63 to 136.37
111.94 to 120.06
112.08 to 119.92
None of the above
The useful life of a certain type of light bulb is known to have a standard deviation of σ = 40 hours. How large a sample should be taken if it is desired to have a margin of error of 10 hours or less at a 95% level of confidence?
8
37
44
62
None of the choices are correct
In determining the sample size, the larger the planning value for p, the larger the sample size.
True
False
A random sample of 300 voters showed 47% in favor of a certain ballot proposal. A 90% confidence interval estimate for the population proportion of voters favoring the proposal is
0.38 to 0.56
0.4226 to 0.5174
0.4412 to 0.4988
0.4136 to 0.5264
None of the above
In choosing a sample size for a public-opinion survey, what hypothesized value of the population proportion will lead to the largest sample size when the confidence level and the maximum sample error are specified?
p = .1
p = .5
p = .99
The confidence level must be known before an answer can be given.