Exam Questions T Test For One Sample Chapter 13 11th Edition

MULTIPLE‑CHOICE TEST ITEMS

CHAPTER 13

t TEST FOR ONE SAMPLE

13.1 Each t distribution is associated with a special number that directly reflects the

a) degrees of freedom.

b) sample size.

c) sample standard deviation.

d) null hypothesized value.

13.2 The t distribution is most different from the standard normal distribution when sample size is

a) infinitely large.

b) very large.

c) large.

d) very small.

13.3 Compared to the normal distribution, a distinctive property of the t distribution is its

a) symmetry.

b) unimodality.

c) bell-shape.

d) inflated tails.

13.4 To save space, t tables supply only critical values of t for a few of the more common

a) levels of significance.

b) null hypotheses.

c) sample sizes.

d) types of investigations.

13.5 The tables for t show

a) critical t values for a single t distribution.

b) positive critical t values for a single t distribution.

c) critical t values for a family of t distributions.

d) positive critical t values for a family t distributions.

13.6 If the desired number of degrees of freedom doesn't appear in the t table, use the critical t associated with

a) the next smallest df in the table.

b) the next largest df in the table.

c) either of the nearest two df entries in the table.

d) a different level of significance.

13.7 Given a critical t of and an observed t of , you should

a) reject the null hypothesis.

b) retain the null hypothesis.

c) postpone any decision.

d) conduct another test, using a larger sample size.

13.8 The estimated standard error of the mean is to be used whenever you must estimate the

a) population mean.

b) sample size.

c) critical t values.

d) population standard deviation.

13.9 To obtain the estimated standard error, divide the sample standard deviation by

a) n

b)

c)

d)

13.10 The major difference between a z ratio and a t ratio is that the t ratio

a) really isn't a ratio.

b) is entirely different.

c) contains extra variability in its denominator.

d) contains an extra component.

13.11 Before the null hypothesis can be rejected at a given level of significance, observed values of the t ratio (compared to those for the z ratio)

a) must deviate further from zero.

b) needn't deviate as far from zero.

c) must deviate the same distance from zero.

d) must deviate from zero.

13.12 To find the appropriate t value for a 95 percent confidence interval, read the t table entry under the column heading that also describes a hypothesis test for a

a) one‑tailed test, .05 level of significance.

b) one‑tailed test, .01 level of significance.

c) two‑tailed test, .05 level of significance.

d) two‑tailed test, .01 level of significance.

13.13 On the basis of a random sample of 25 students from a large university, an educator estimates, with 95 percent confidence, that between 17 to 20 hours describes the mean weekly study time of all students at the university. Accordingly, we can be reasonably certain that

a) 95 percent of all students study between 17 and 20 hours.

b) on average, all students study between 17 and 20 hours.

c) the sample mean (for the 25 students) was between 17 and 20 hours.

d) all of the above

13.14 Even when the normality assumption is violated, the t test retains much of its accuracy as long as the

a) population standard deviation is known.

b) sample size isn't too small.

c) observed value of t isn't too large.

d) sample standard deviation isn't too small.

13.15 Degrees of freedom refer to the number of values that are free to vary, given

a) the range of possible values.

b) one or more mathematical restrictions.

c) that each value is independent of all other values.

d) that all values contribute equally.

Ans; b

13.16 When using the t test for a single population mean, a single degree of freedom is lost. Therefore one is subtracted from the

a) standard error.

b) standard deviation.

c) sample size.

d) observed t.

13.17 The loss of a single degree of freedom occurs for the t test for a single population mean because only n ‑ 1 of the observations

a) are valid.

b) are known.

c) vary about the population mean.

d) supply information about population variability.

13.18 Given that three gas mileage tests yield a mean of 30 miles per gallon, and that two of the tests have values of 27 and 29, the third test must have a value of

a) 28.5

b) 30

c) 32

d) 34

13.19 Even though there are n deviations in a sample, only n ‑ 1 of these deviations supply a true picture of the population deviations because only n ‑ 1 are free to vary, given that the sum of

a) n deviations from their own sample mean always equals zero.

b) n deviations from their own population mean always equals zero.

c) n ‑ 1 deviations from their own sample mean always equals zero.

d) n‑ 1 deviations from their own population mean always equals zero.

13.20 A property of all hypothesis tests is that

a) common outcomes cause the null hypothesis to be rejected.

b) rare outcomes cause the null hypothesis to be rejected.

c) common outcomes occur about as often as rare outcomes.

d) rare outcomes could reflect an unduly small sample size.

13.21 A tire manufacturer wishes to determine whether, on average, a steel‑belted radial tire provides more than 50,000 miles of wear. A random sample yields a sample mean of 53,500 miles and a standard deviation of 5,300 miles. From the manufacturer's perspective, it would be best if the sample size were

a) 20

b) 30

c) 40

d) 50

13.22 Even though the population standard deviation is unknown, an investigator uses z rather than the more appropriate t to test a hypothesis at the .01 level of significance. In this situation the true level of significance is

a) smaller than .01.

b) equal to .01.

c) larger than .01.

d) unknown.