Psych Stats Test 2
Which z-score corresponds to a score that is above the mean by 2 standard deviation?
+2
Which statement below accurately describes the relationship between the alpha level, the size of the critical region, and the risk of a Type I error?
As the alpha level increases, the size of the critical region increases, and the risk of a Type I error increases
Which of the following is a requirement for a random sample?
Every choice is correct
All random samples of size n = 9 are selected from a normal population with µ = 55 and σ = 10, and the mean is computed for each sample. Then, all the possible samples of size n = 36 are selected from the same population, and the mean is computed for each sample. Which statement below is true?
The distribution of sample means for samples of n = 36 is less variable than the distribution of sample means for n = 9.
Which statement below is not consistent with the distribution of sample means?
The distribution of sample means tends to pile up around the population standard deviation
A researcher chooses to collect data from a large sample that represents a population instead of a smaller sample. Which of the following is not a likely consequence of choosing to collect data from a large sample relative to a smaller sample?
The expected value of M will decrease.
A sample of n = 25 individuals is selected from a population with µ = 80, and a treatment is administered to the sample. Which outcome is expected if the treatment has no effect?
The sample mean after the treatment should be close to 80, leading a researcher to fail to reject the null hypothesis.
Which of the following statements correctly describes the effect of increasing the alpha level (for example, from a = 0.01 to a = 0.05)
This action increases the likelihood of rejecting H0 and increases the risk of a Type I error
Under which circumstance will the distribution of sample means be normal?
if the population is normal or if the sample size is greater than 30
When a sample size from a population is n = 1, then the standard error will always equal the _____. a. population standard deviation
population mean
A researcher expects a treatment to increase the scores for individuals in a population. The treatment is evaluated using a one-tailed hypothesis test, and the test produces z = +2.40. Based on this result, which is the correct statistical decision?
reject the null hypothesis with either α = 0.05 or α = 0.01
Which of the following is an accurate definition of a Type I error?
rejecting a true null hypothesis
Transforming a set of scores into a standardized distribution of z-scores consists of graphically _____ the score
relabeling
A hypothesis test involves a comparison of which two elements?
research results from a sample and a hypothesis about a population
Which is the standard error of M?
the standard deviation of the distribution of sample means
For a distribution of scores, the location identified by z = +1.00 and the location identified by z = -1.00 are the same distance from the mean.
true
A class consists of 10 male students and 30 female students. If one student is randomly selected from the class, what is the probability of selecting a male student?
10/40
Scores on the SAT form a normal distribution with a mean of µ = 500 and standard deviation of σ = 100. If the state college only accepts students who score in the top 60% on the SAT, what is the minimum score needed to be accepted?
475
A treatment is administered to a sample of n = 9 individuals selected from a population with a mean of µ = 80 and a standard deviation of σ = 12. After treatment, the effect size is measured by computing Cohen's d, and a value of d = 0.50 is obtained. Based on this information, what is the mean for the treated sample?
M=86
Which statement accurately describes the proportions in the tails of a normal distribution?
Proportions in both tails are the same
Which statement accurately describes the proportions in the tails of a normal distribution?
Proportions in both the left-hand and right-hand tails tend to be relatively small
Last week, Sarah had exams in her math and Spanish classes. On the math exam, the mean was µ = 30 with σ = 5, and Sarah had a score of X = 45. On the Spanish exam, the mean was µ = 60 with σ = 8, and Sarah had a score of X = 68. For which class should Sarah expect the better grade relative to her peers in each class?
Spanish
A sample is selected from a normal population with a mean of µ = 40. If the sample mean is M = 45, which of the following combinations would make the sample mean an extreme, unrepresentative value for the population?
a large sample and a small population standard deviation
Z-scores are useful with regard to inferential statistics primarily because they offer a tool by which to determine whether _____.
a sample is noticeably different from a population
A sample is selected from a normal population with a mean of µ = 40. If the sample mean is M = 45, which of the following combinations would make the sample mean a typical, representative value for the population?
a small sample and a large population standard deviation
Which of the following accurately describes a hypothesis test?
a statistical technique that uses the data from a sample to evaluate a hypothesis about a population
Which position in a distribution corresponds to a z-score of z = -1.00?
below the mean by 1 standard deviation
Even if a treatment has an effect, it is still possible to obtain a sample mean after the treatment that is very similar to the original population mean. Which outcome is likely if this happens?
fail to reject H0 and make a Type II error
Which of the following is an accurate definition of a Type II error?
failing to reject a false null hypothesis
Consider a researcher who is conducting final clinical trials to validate that a new treatment for anxiety is effective. This researcher is extremely focused on avoiding mistakes in concluding that this new treatment is effective when it really is not when conducting their research. What should this researcher do?
set a low alpha level
What is measured by the denominator of the z-score test statistic?
the amount of error expected between the sample mean and hypothesized population mean
Which is the expected value of M?
the mean of the distribution of sample means
Which of the following is directly communicated within the null hypothesis?
the population mean after treatment
Under which circumstance is a score that is 15 points above the mean an extreme score relatively far from the mean?
when the population standard deviation is much smaller than 15
When is a researcher at risk of making a Type I error?
whenever H0 is rejected
A sample of n = 20 scores has a mean of M = 32 and a standard deviation of s = 6. In this sample, what is the z-score corresponding to X = 28?
z = -0.67
Which z-score value represents the location farthest from the mean?
z = -2.00
A sample of n = 4 scores with M = 43 is selected from a normal population with µ = 40 and with σ = 8. What is the expected value for the sample mean?
µM = 40
Samples of size n = 9 are selected from a normal population with µ = 80 and with σ = 18. What is the expected value for the mean of the distribution of sample means?
µM = 80
Which symbol is used to identify the standard error of M?
σM
