Question | Answer |
(Sm) used as an estimate of the real standard error (Om), when the value of O is unknown. Computed from the sample variance or sample standard deviation and provides an estimate of the standard distance between a sample mean M and the population mean U. | estimated standard error |
used to test hypotheses about an unknown population mean, U, when the value of O is unknown. | t statistic |
describes the number of scores in a sample that are independent and free to vary. (n -1) | degrees of freedom |
the complete set of t values computed for every possible random sample size (n) or a specific degrees of freedom (df). Approximates the shape of normal distribution. | t distribution |
Under what circumstances is a t statistic used instead of a z-score for a hypothesis test? | A t statistic is used instead of a z-score when the population standard deviation and variance are not known. |
A sample of n=9 scores has SS = 288. Compute the variance for the sample. | 36 |
A sample of n=9 scores has SS = 288. Compute the estimated standard error for the sample mean. | 2 |
True or False. In general a distribution of t statistics is flatter and more spread out than the standard normal distribution. | True - As sample size and df increase, the variability in the t distribution decreases, and more closely resembles a normal distribution. |
A researcher reports a t statistic with df = 20. How many individuals participated in the study. | n = 21 |
For df=15, find the value(s) of t associated with the top 5% of the distribution. | +1.753 |
For df=15, find the value(s) of t associated with the middle 95% of the distribution. | +-2.131 |
For df=15, find the value(s) of t associated with the middle 99% of the distribution. | +-2.947 |
Sample = n=4, U=40 Treatment sample = M=44, variance s2=16. Is this sample sufficient to conclude that the treatment has a significant effect? | No - Fail to reject H0, treatment does not have a significant effect |
Sample = n=4, U=40 Treatment sample = M=44, variance s2=16. If all factors remained constant and sample size increased to n = 16, is sample sufficient to prove significant effect? | Yes, Reject NO. Treatment has significant effect. |
an interval or range of values, centered around a sample statistic. | confidence interval |
If all other factors are held constant, an 80% confidence interval is wider than a 90% confidence interval. (True or False?) | False - Greater confidence requires wider interval. |
If all other factors are held constant, a confidence interval computed from a sample of n=25 is wider than a confidence interal computed from a sample of n = 100. | True. The smaller sample produces a wider interval. |