Chapter 9 PY 211 True/False
A one-sample t test will be undefined (denominator = 0) when the same score is recorded for all participants in a study.
TRUE
A one-sample t-test will be t = 0 when the mean difference is equal to 0
TRUE
An estimated Cohen's d is interpreted in terms of the number of standard deviations that an effect shifted in some population
TRUE
Measures of proportion of variance are computed the same for all t-tests
TRUE
A researcher computes a two-independent sample t test and finds that the result is undefined (the denominator is equal to 0). this happens when there is no difference between the two groups (i.e. the mean difference is equal to 0)
FALSE
A researcher must know the population variance in order to compute a t-test
FALSE
A t distribution with infinite degrees of freedom is a z distribution
TRUE
A t statistic estimates the standard error by using the sample variance to approximate the population variance
TRUE
A t test is associated with n-1 degrees of freedom
TRUE
A researcher reports the following result for a lower-tail critical test at .05 level of significance t(40) = 3.212 and accurately concludes that this result is significant
FALSE
A researcher reports the following result for a two-tailed test at .05 level of significance t(24) = 2.010 and correctly decides to reject the null hypothesis
FALSE
A researcher reports the following result for a two-tailed test at a .05 level of significance, t(30) = 2.320 and correctly decides to retain the null hypothesis
FALSE
A two-independent sample t test is computed when mean differences are compared between two or more groups sampled from a population with an unknown variance
FALSE
A two-independent sample t test is used when the same participants are observed in each of two groups
FALSE
As the degrees of freedom for a t test increase, the critical values for that test also increase
FALSE
If d = 0.28, then we conclude that mean scores in some population have shifted 0.28 standard deviations below the mean
FALSE
The critical values are reported with the test statistic of a one-sample and a two-independent sample t test using APA format
FALSE
When the difference between two groups is compared, the pooled standard deviation is used as an estimate for the population standard deviation in the effect size formula for estimated Cohen's d
TRUE
A t test is associated with N degrees of freedom
FALSE
Normality is the assumption that data in the population are normally distributed
TRUE
When testing a hypothesis with one or two groups selected from a population with an unknown variance, a t test is appropriate
TRUE
When the proportion of variance explained by some treatment is larger than 0.25, we conclude that there is a large effect in the population
TRUE
A one-sample t test will be t = 0 when the standard error was equal to 0
FALSE
Cohen's d is a measure of proportion of variance
FALSE
A researcher reports that the mean difference between two groups is 20.12 and the estimated standard error for the difference is 2.83. hence, the conclusion must be to reject the null hypothesis for a two-tailed test at a .05 level of significance
TRUE
Effect size measures are an estimate of the size of an effect in a population
TRUE
When scores are measured in a single group, the sample standard deviation is used as an estimate of the population standard deviation in the effect size formula for estimated Cohen's d
TRUE
Eta-squared is a more conservative estimate than omega-squared
FALSE
The p value is reported with the test statistic of a one-sample and a two-independent sample t-test using APA format
TRUE
Normality, random sampling and independence are all assumptions for the one-sample t-test
TRUE
