Ch 7, 8, & 9 trial exam
(22) On average, what value is expected for the t statistic when the null hypothesis is true?
0
(10) A random sample of n =4 scores is obtained from a normal population with µ = 20 and σ = 4. What is the probability of obtaining a mean greater than M = 22 for this sample?
0.1587
(19) A sample of n = 25 individuals is selected from a population with µ = 60 and σ = 10 and a treatment is administrated to the sample. After treatment, the sample mean is M = 63. What is the value of Cohen's d for this sample?
0.30
(21) A sample of n = 4 scores has SS = 48. What is the variance for this sample?
16
(4) If random samples, each with n = 25 scores, are selected from a normal population with µ = 80 and σ = 20, and the mean is calculated for each sample, then the average distance between M and µ would be ___.
4 points
(11) The null hypothesis ___.
All of the other choices are correct [ANS: concerns a population with an unknown mean; is denoted by the symbol H₀; generally states that there is no effect, no change, or no difference]
(20) Which of the following is a major difference between a hypothesis test with the t statistic formula and the test with a z-score?
All of the other options are major differences [ANS: You must calculate the sample variance (or standard deviation) for the t statistic but not for the z-score; you must know the population variance (or standard deviation) for the z-score but not for the t statistic; you use the unit normal table to find critical values for the z-score test but not that t-test]
(30) As sample size increases
All of the other options are true as sample size increases [ANS: the value of df also increases; the t distribution becomes more like a normal distribution; the critical values of t move become smaller]
(27) A sample is selected from a population with µ = 80, and treatment is administrated 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
(16) A researcher conducts a hypothesis test to evaluate the effect the effect of a treatment. The hypothesis test produces a z-score of z = -2.40. Assuming that the researcher is using a two-tail test, what is the correct statistical decision?
Reject the null hypothesis with α = .05 but not with α = .01
(32) As the sample size increases, what happens to the measures of effect size such as r² and Cohen's d?
Sample size does not have any great influence on measures of effect size
(31) A sample of n = 25 scores produces a t statistic of t = -2.06. If the researcher is using a two-tailed test with α = .05, the correct statistical decision is ___.
The researcher must fail to reject the null hypothesis with either α = .05 or α = .01
(17) A researcher expects a treatment to produce an increase in the population. The treatment is evaluated using a one-tailed hypothesis test, and the test produces z = -1.85. Based on this result, what is the correct statistical decision?
The researcher should fail to reject H₀ with either α = .05 or α = .01
(26) Which set of sample characteristics is most likely to produce a significant t statistic?
a large sample size and a small sample variance
(25) Which set of sample characteristic is most likely to produce a larger value for the estimated standard error?
a small sample size and a large sample variance
(14) Which combination of factors will increase the chances of rejecting the null hypothesis?
a small standard error and a large alpha level
(5) If two samples of exactly the same size are selected from the same population, then the two sample means will have ___.
exactly the same expected value and exactly the same standard error
(15) A Type II error that a researcher has ___.
falsely conducted that a treatment has no effect
(13) In general, increasing the sample size (for example, from n =4 to n = 50) will ___ the risk of a Type I error.
have no influence on
(23) The estimated standard error, sM, provides a measure of
how much difference is reasonable to expect between the sample mean and the population mean
(8) If sample size (n) is held constant, the standard error will ___ as the population variance increases.
increase
(24) The size of the estimated standard error is ___.
inversely related to the sample size and directly related to the sample variance
(7) In general, the standard error of M gets smaller as ___.
sample size increases and standard deviation decreases
(12) In a hypothesis test, the critical region consists of ___.
sample values that are very unlikely to be obtained if H₀ is true
(6) As sample size increases, the expected value of M ___.
stays constant
(28) What is the sample variance and the estimated standard error for a sample of n = 4 scores with SS = 300?
s² = 100 and sM = 5
(29) What t values define the critical region for a regular two-tailed test using a sample of n = 25 scores and an alpha level of .05?
t = ±2.064
(2) When the sample size is greater than n = 30 ___.
the distribution of sample means will be approximately normal
(3) When a random sample is selected from a population, the sample mean is not expected to be exactly equal to the population mean. On average, the size of the difference between the sample mean and the population mean is predicted by ___.
the standard error
(1) The standard deviation of the distribution of sample means is called ___.
the standard error of M
(9) A random sample of n = 9 scores is obtained from a population with µ = 50 and σ = 9. If the sample mean is M = 53, what is the z-score corresponding to the sample mean?
z = 1.00
(18) A population is know to have a mean of µ = 50. A treatment is expected to increase scores for individuals in this population. If the treatment is evaluated using one-tailed hypothesis, then the null hypothesis would state ___.
µ ≤ 50