38. A random sample of 25 automobiles traveling on a section of an interstate sh

Question

38. A random sample of 25 automobiles traveling on a section of an interstate showed an average speed of 60 mph and a sample standard deviation of 10 mph. Assume the distribution of speeds of all the cars is normal. If we are interested in determining an interval estimate for
at 95% confidence, we should use

Z0.025

t0.025, 25

t0.05, 24

t0.025, 24

39.

A random sample of 25 automobiles traveling on a section of an interstate showed an average speed of 60 mph and a sample standard deviation of 10 mph. Assume the distribution of speeds of all the cars is normal. The 95% confidence interval estimate for unknown
is

60 ±3.422 mph

60 ±3.416 mph

60 ±4.128 mph

60 ±4.120 mph

40. A random sample of 25 automobiles traveling on a section of an interstate showed an average speed of 60 mph and a sample standard deviation of 10 mph. Assume the distribution of speeds of all the cars is normal. Compared with the 95% confidence interval, the 80% confidence interval estimate for unknown must be

obtained by statistical software operation such as MS Excel.

wider than the 95% confidence level interval estimate.

enlarged by an increasing sample size.

narrower than the 70% confidence level interval.

Z0.025

t0.025, 25

t0.05, 24

t0.025, 24

Explanation / Answer

38) Option-D)

39) Option-C).

40) Option-C)

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