Chapter 9 Review

With @=.05, the two tailed critical region for a test using a sample of n=20 participants would have boundaries of _________.

t=+/-2.093

All else constant, which combination of factors would increase the width of a confidence interval most?

A smaller sample size and a larger confidence interval

A hypothesis test produces a t statistic of t=+2.19. If the researcher is conducting a two-tailed hypothesis test with @=.05, how large does the sample have to be in order to reject the null hypothesis?

At least n=13

Which bit of information is not obtainable from the results of a t-test written up in a statistical report?

Each of these bits of information is obtainable from the results of a t-test written up in a statistical report

Under what circumstances can a very small treatment effect be statistically significant?

If the sample size is large and the sample variance is small

When n is small (less than 30), how does the shape of the 't' distribution compare to the normal distribution?

It is flatter and more spread out than the normal distribution

How does sample variance influence the estimated standard error and measures of effect size such as r^2 and Cohen's d?

Larger sample variance increases the estimated standard error but decreases measures of effect size

If a treatment is expected to increase scores on a variable for which the mean is expected to be Mew=100, what is the null hypothesis?

Mew(with treatment) <(or equal to)100

Which situation below violates an assumption for conducting hypothesis tests using the t statistic?

None of these situations violates an assumption for conducting hypothesis tests using the t statistic

Which of the following is a fundamental difference between a 't' statistic and a z-score?

The 't' statistic uses the sample variance in place of the population variance

Assuming all other factors are held consistent, if the df value for a two-tailed t-test with @=.05 were increased from df=6 to df=20 what would happen to the critical values for t?

The critical values would move closer to t=0

Which of the following is consistent with what r^2 represents as a measure of effect size?

The portion of variability in a sample attributable to a treatment effect relative to the total variability in the sample

The results of a hypothesis test are reported as follows in a scientific report: t(17)=+2.76, p<.05. Based on this information, which statement below is not correct?

The probability that there is a statistically significant effect is less than 5%

If a researcher is using a 't' statistic to test a null hypothesis about a population, what information is needed from the population to calculate the 't' statistic?

The researcher does not need to know any information about the population

A sample of n=25 scores produces a t statistic of t=+2.05. If the researcher is conducting a two-tailed hypothesis test, which of the following is the correct statistical decision?

The researcher should fail to reject the null hypothesis with either @=.05 or @=.01

If n=63 for a two-tailed hypothesis test in which a t-test should be utilized, which df value should be referenced when using the abridged t distribution table in the textbook in order to set the critical t values for the hypothesis test?

df=60

Which of the following samples will have the smallest value for the estimated standard error?

n=16 with s^2=16

Which of the following results from a hypothesis test involving the computation of a t-statistic is structured correctly based on standards for presenting hypothesis tests in scientific reports?

t(19)=2.30, p<.05, r^2=0.42