The _______ confidence interval for the population mean is always wider than the _______ confidence interval for the population mean.
a. 99; 95 c. both of these
b. 95; 99 d. none of these
If the population parameters are known, the t test is _________ powerful than the z test.
a. more c. equally
b. less d. need more information
As N gets infinitely large, the critical value of t equals the critical value of z.
a. true b. false
As N gets _______, the critical value of t gets _________.
a. larger; larger c. larger; smaller
b. smaller; smaller d. smaller; larger
For a given value of alpha, the critical value of t is _______ than the critical value of z.
a. no different c. greater
b. less d. none of these
How many t distributions are there?
a. 1 c. 30
b. 2 d. one for each value of df
A researcher believes that women today weigh less than in previous years. To investigate this belief, she randomly samples 41 adult women and records their weights. The scores have a mean of 111 lbs. and a standard deviation of 12.4 . A local census taken several years ago shows the mean weight of adult women was 115 lbs. The df for determining tcrit = _________.
a. 41 c. 39
b. 40 d. need more information
The confidence interval for the population mean is _________.
a. a range of values which probably contains the population mean
b. a range of values which contains the population mean
c. the same from sample-to-sample
d. a range of values which probably contains the population meanand the same from sample-to-sample
As the degrees of freedom increase, the correspondence between the t and z distributions _________.
a. increases c. remains the same
b. decreases d. cannot be determined
In a correlated groups experiment, if we must estimate the population standard deviation to determine the significance of the sample results, the appropriate statistical test is _________.
a. t test c. z test
b. sign test d. none of these
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