Unit 4 Flashcards
A “significant” event in statistics is one that is
not attributed to chance
Maximizing the power of an experiment ____.
minimizes beta
Which of the following studies uses a matched-subjects design?
Participants are assigned to one of two treatment groups so that each participant in one group has the same IQ as a participant in the other group.
“The difference between the two __________ means is zero” is a statement of the null hypothesis.
population
In general, the z test is more powerful than the t test because ____.
with the z test, we know sigma, whereas with the t test, we must estimate it.
A sample is selected from a population and a treatment is administered to the sample. If there is a 5 point difference between the sample mean and the original population mean, which set of sample characteristics is most likely to lead to a decision that there is a significant treatment effect?
small variance for a large sample
A Type II error is not possible
when you have rejected the null hypothesis
The area under the critical region for rejection must ____.
equal alpha
If the population parameters are known, the t test is ____ powerful than the z test.
less
The sampling distribution of t depends on ____.
df
An increase from smaller to larger in which of the following would produce a more powerful statistical test?
alpha
The t distribution is a sampling distribution based on the assumption that the __________ hypothesis is __________.
null, true
The null hypothesis is a hypothesis about
the population
Other things being equal, the critical value for a directional test is ____ the critical value for a nondirectional test.
smaller than
An increase from smaller to larger in which of the following would produce a more powerful statistical test?
N
For a repeated-measures hypothesis test, the null hypothesis states __________.
μD = 0
Degrees of freedom are most closely related to
sample size
The t distribution is a(n) __________ sampling distribution based on the assumption that the null hypothesis is __________.
theoretical, true
Drugs used in treating schizophrenia all block the reception of dopamine by neurons. (Dopamine is a neurotransmitter, which, when released by the axons of one nerve, inhibits the firing of the next nerve.) This fact led to the idea that schizophrenia occurs when too much dopamine is produced. Suppose the following data on dopamine production were obtained. This is an example of
independant-samples
A t test value that is smaller than the tabled value of t
leads to a failure to reject the null hypothesis
The rule that governs degrees of freedom is that
df depends on the number of observations minus the number of parameters estimated with statistics
The advantage of a powerful experiment is that ____.
you are more likely to detect the real effects of the independent variable, if there are any.
95 children are placed in one group and a sibling of each child is placed in another group. Both groups are tested on a measure of aggression. What type of samples are being used?
correlated samples
This question requires you to examine the formulas for the standard error of a difference between means. If calculated on the same data, the paired-samples version will be smaller than the independent-samples version except when
r is -
The statistical technique of null hypothesis statistical testing is designed to test a hypothesis about
a population parameter
The denominator of a test statistic for computing the means of two independent samples is called the ____.
standard error of the difference between two means
Which phrase goes with “in the rejection region”?
The calculated probability is small
The power of a correlated t test increases if the correlation between the paired scores is ____.
high
Assuming that other factors are held constant, which of the following would tend to decrease the value of the t statistic (make it closer to zero)?
Increase in sample variance
A researcher reports t(24) = 5.30 for an independent-sample differences between means t test. How many individuals participated in the entire experiment?
26
Which of the following research situations is most likely to use an independent-samples design?
Evaluate the difference in verbal skills between 3-year-old girls and 3-year-old boys.
Even a very small treatment effect can be statistically significant if __________.
the sample size is big and the sample variance is small
An independent-samples experiment uses two samples with n = 7 in each to compare two experimental treatments. The t statistic from this experiment will have degrees of freedom equal to __________.
12
Suppose a two-independent sample t-test were performed on the data shown below at left; and another t test were performed on the data shown below at right.
the t value on the right would be larger
The t distribution, as a sampling distribution, gives the probability of events when
The null hypothesis is true
If you find that there is a logical reason to pair the scores from the two groups in a two-group experiment, you know whether
the design is a paired-samples or an independent-samples design
Which of the following terms is not required when using the t statistic?
sigma
If the t distribution is to produce an accurate probability figure for an independent-samples t test, which of the following must be true?
the populations the samples are from must have equal variances
If one draws two samples of size N from a distribution of raw scores (with replacement), then the means of the two samples will ____.
perhaps be equal but not necessarily
A repeated-measures experiment and an independent-measures experiment both produce t statistics with df = 20. Which experiment used more subjects?
independant measure
Sample scores: 2, 3, 4
The t value when the scores in Data Set 8-1 are tested against H0: µ = 1.00 leads to the conclusion that the null hypothesis be
rejected at the .05 level for a one-tailed test
The null hypothesis for a nondirectional H1 using the t test for correlated groups asserts that ____.
µD = 0
To calculate a t statistic for a specific sample, what information is needed about the population from which the sample was obtained?
the value for mew
A student conducted a before and after study on college statistics students to see if the course improved ability to reason. In a later study, she used a mother-daughter sample to assess generational differences in attitudes toward abortion. Her two designs are
paired, paired
A researcher is interested in the effect of a particular exercise on health. Perhaps this exercise will improve health, perhaps it will cause health to deteriorate. He identifies 20 pairs of identical twins. For each set of twins, one twin is enrolled in a home exercise training program while the other twin receives placebo home visits. The dependent variable is the number of days missed from school or work over a two-year period. This study is best considered to be
a nondirectional dependent sample design
The concept of using sample data to tell you whether the sample came from a hypothesized population is called
null hypothesis statistical testing
A hypothesis about a mean was proposed, an alpha level of .05 adopted, data gathered, a sample mean computed, and a probability figure attached to the difference between the sample mean and the hypothesized mean. Which of the following probabilities are in the rejection region?
none of the above
A repeated-measures experiment and a matched-subjects experiment both produce t statistics with df = 20. Which experiment used more subjects?
matched subjects
In an independent groups experiment, if we must estimate the population standard deviation to determine the significance of the sample results, the appropriate inference test is the ____.
t test
Which of the following is an example of correlated samples?
Husbands and wives
A t test value that is smaller than the tabled value of t
leads to a failure to reject the null hypothesis and
has a probability greater than α, if the null hypothesis is true
A sample is selected from a population with = 80, and a treatment is administered to the sample. If the sample variance is s2 = 20, which set of sample characteristics is most likely to lead to a decision that there is a significant treatment effect?
M = 90 for a sample of n = 100
In a two-tailed test of significance,
the critical region is assigned to two places on the sampling distribution
As the df increases, the t distribution ____.
approaches the normal distribution
The logic of hypothesis testing is to assume that two populations have
means that are equal and then see if sample data will permit you to conclude that they are probably unequal
A hypothesis test with a sample of n = 25 participants produces a t statistic of t = 2.53. Assuming a two-tailed test,
The researcher can reject the null hypothesis with = .05 but not with = .01.
The standard error of the difference of the data in Data Set 9-7 is
none of the above
Scores: 1, 2, 3, 4, 5
Test the scores in Data Set 8-2 against H0:μ = 4.00. The t value that results is
1.41
Sample scores: 2, 3, 4
The value of the standard error of the mean for the scores in Data Set 8-1 is
0.577
The proper conclusion from Data Set 9-8 is that
there is no significant difference in the effect of the two drugs on emotionality
Using the population of Exhibit 12-1, what is the probability of randomly selecting a sample of 30 scores which has a mean attention span equal to or greater than 17 minutes?
0.0436
A t test value that is larger than the tabled value of t
leads to rejection of the null hypothesis
and has a probability less than alpha, if the null hypothesis is true
The reason for not reducing the α level to one in a million or even less is that
β would be too large
In a paired-samples design, the Apple mean was 6 and the Orange mean was 7. An α level of .05 was adopted; the data produced a t value of 2.15. Which conclusion is appropriate for a two-tailed test?
If df = 15, Oranges are significantly greater than Apples
Which of the following is a correct pairing?
Type I error, alpha
1 - beta is the __________ of a statistical test.
power
For a normally distributed set of scores, it is often best to use the design that has the most power. Which of the following designs has the most power?
paired sample
For the z test, the critical region for rejection of H0 ____.
is determined only by α
The rule that governs degrees of freedom is that
df depends on the number of observations minus the number of parameters estimated with statistics
A t test value that is larger than the tabled value of t
has a probability less than alpha
With = .05, the critical values for a two-tailed z-score test are 1.96. The corresponding values for a two-tailed t test with = .05 tend to be __________.
greater than 1.96 (farther from zero)
After calculating the appropriate statistics you find that this value has a p < .05 which means that
the null hypothesis should be rejected and
the difference analyzed by a t test is statistically significant
For a simple experiment, which of the following is true?
Treat both groups exactly alike except for one thing
How many t distributions are there?
one for each value of df
One can increase power by ____.
increasing N and
increasing the effect of independent variable
