Question

15. Which of the following statement regarding t and z distributions is incorrect ___________?

a. z distribution is also called standardized normal distribution

b. z critical values are determined by the z distribution and the alpha level

c. t distribution is a family of distribution, one for each degrees of freedom

d. t critical values are determined by the t distribution and the alpha level

16. When n is small (less than 30), the t distribution ______.

a.         is almost identical in shape to the normal z distribution

b.         is flatter and more spread out than the normal z distribution

c.         is taller and narrower than the normal z distribution

d.         Has a bimodal distribution, with two peaks

17. If a researcher reports a single sample t statistic with df =79, how many individuals were in the sample?

a. n=78

b. n=79

c. n=80

18. Independent-samples study uses one sample with n = 30 and a second sample with n = 45 to compare two experimental treatments.  The t statistic from this experiment will have degrees of freedom equal to ______.

a.         72

b.         73

c.         74

d.         75

19. For which of the following situations would a repeated-measures research design be appropriate____?

a.         Comparing incoming ACT and SAT scores from prospective students who took one or the other

b.         Comparing test scores before and after someone drinks a cup of coffee

c.         Comparing test scores of collegiate athletes and nonathletes

d.         Comparing problem solving skills for high school students and undergraduate college students in a cross-sectional study

20. Which of the following statement is incorrect regarding alpha level ___________?

a. alpha level is specified by the researcher

b. alpha level is a probability

c. alpha level is used to determine critical values for both t and z tests

d. decreasing alpha level increases the chance of rejecting the null hypotheses

Answer 1

15. Which of the following statement regarding t and z distributions is incorrect ___________?

c. t distribution is a family of distribution, one for each degrees of freedom

16. t-distribution is less peaked than standard normal distribution at the center and higher in tails, thus t-distribution is platykurtic.

Therefore when n is small (less than 30), the t distribution ______.

b.         is flatter and more spread out than the normal z distribution

17. If a researcher reports a single sample t statistic with df =79, how many individuals were in the sample?

c. n=80

18. Independent-samples study uses one sample with n = 30 and a second sample with n = 45 to compare two experimental treatments.  The t statistic from this experiment will have degrees of freedom equal to 30+45-2=73.

b.         73

19. For which of the following situations would a repeated-measures research design be appropriate____?

b.         Comparing test scores before and after someone drinks a cup of coffee

[Note: repeated-measures research design uses the same subjects with every branch of research, including the control. For instance, repeated measurements are collected in a longitudinal study in which change over time is assessed]

20. Which of the following statement is incorrect regarding alpha level ___________?

d. decreasing alpha level increases the chance of rejecting the null hypotheses

[alpha level is upper bound of probability of type I error i.e. we reject null hypothesis when it is true, so if we decrease aplha level then the rejection region is also decreased hence chance of rejecting null hypothesis is also decreased.]