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Homework answers / question archive / Psyc 233 Exam 3 Online Part I
Psyc 233 Exam 3 Online
Part I. Multiple Choice
For each question choose the BEST alternative. Type your answer in the blank before each question.
__C___1. Which alpha level will reduce Beta (β) most?
a. .01
b. .025
c. .05
d. alpha has no impact on Beta (β)
_B____2. A researcher conducts a test to see if a new Alzheimer drug improves memory function. She rejects the research hypothesis because her obtained Z-value was 3.65 compared to the critical value of Zcritical = 2.33 for her one-tail test at alpha α = .01. Which of the following is in error in the above problem?
a. The researcher used the wrong critical value
b. The researcher tested the wrong hypothesis
c. .The researcher must have made a Type I error
d. There is no error
__D___3. Which of the following would represent a Type I error?
a. testing negative for HIV and being HIV negative
b. .testing negative for HIV and being HIV positive
c. testing positive for HIV and being HIV positive
d. testing positive for HIV and being HIV negative
___C___4. When testing a hypothesis we try to __________ the _________ hypothesis in order to indirectly support the _________ hypothesis.
a. prove; null; research
b. prove; research; null
c. disprove; null; research
d. disprove; research; null
___B__5. A two-tailed, non-directional test was performed on a sample with 
and n = 36, and the obtained (calculated) z-score was -2.01. Which of the following is the correct decision?
a. reject H0 either with α = .05 or α = .01
b. reject H0 if α = .05, but not if a = .01
c. fail to reject H0 either with α = .05 or α = .01
d. not able to make decision because of insufficient information
_B____6. A population of immigrants represented by a sample of N=16 is compared to the general population (m = 68 and s = 20). What will the standard error for the test be?
__C___7. If I form a sampling distribution of the mean from a population with a μ = 12.8, what value will the mean of that distribution have?
d. 5.24
___A__8. A researcher conducts a test and rejects the null hypothesis. In reality the null hypothesis was true. Which type of error did she commit?
a. Type I
b. Type II
c. Type III
d. a correct decision was made (no error)
__B___9. Holding everything else constant, increasing the sample size will _________ the value of the z-statistic and __________ the number of hypotheses rejected.
a. increase; decrease
b. increase; increase
c. decrease; decrease
d. decrease; increase
___D__10. There is always a chance we will make an error testing a hypothesis, but researchers should always try to minimize the chance of ______________:
a. Type I errors
b. Type II errors
c. correct decisions
d. Type I errors in some situations and Type II errors in other situations
___B__11. Indirect support for the research hypothesis is found when we:
a. reject the research hypothesis
b. reject the null hypothesis
c. retain or fail to reject the research hypothesis
d. retain or fail to reject the null hypothesis
__C___12. Anything that increases the value of the z-statistic we compute:
a. increases the chance we reject the null and decreases Type I errors
b. increases the chance we reject the null and increases Type I errors
a. increases the chance we reject the null but has no effect on Type I errors
a. has no effect on the chance we reject the null or Type I errors
__A___13. False positive results are the same as __________ errors, and false negative results are the same as ________ errors.
a. Type I; Type II
b. Type II, Type I
c. Type I; Type I
d. Type II; Type II
A researcher is interested in studying whether caffeine improves intelligence. He gives his students 300mg of caffeine and tests their average IQ (X
= 102) against that of the general population (µ = 100). He ends up rejecting the null hypothesis.
__A___14. The researcher is testing a __________ hypothesis
a. directional
b. non-directional
c. two-tail
d. research
__C___15. Based on the researcher’s decision about the null, we can conclude:
a. caffeine has no effect on intelligence
b. caffeine reduces intelligence
c. caffeine improves intelligence
d. cannot be determined from the information given
___ µcaffeine ≤ 100__16. Which of the following would represent the null hypothesis?
a. µcaffeine ≠ 100
b. µcaffeine ≠ 102
c. µgeneral ≠ 100
d. µgeneral ≠ 102
___B__17. Which of the following is the correct research hypothesis?
a. students taking caffeine will have lower IQ scores than the general population
b. students taking caffeine will have higher IQ scores than the general population
c. students taking caffeine will have the same IQ scores as the general population
d. students taking caffeine will have the same or lower IQ scores as the general population
___A__18. How does decreasing the sample size affect the standard error?
a. it increases the standard error
b. it decreases the standard error
c. it has no effect on the standard error
d. cannot be determined because it depends on the problem
____A__19. Which of the following would be the research hypothesis?
a. Children who go to Head Start programs will learn to read sooner than children
who do not go
b. There will be no difference in learning to read between children who go to Head Start
programs and children who do not go
c. Ages of children must be equated to insure there are no differences due to
maturation level
d. An unbiased random sample must be obtained prior to conducting the research
___A___20. A Type I error can occur only if the:
a. null hypothesis was rejected
b. null hypothesis was retained
c. sample size is small
d. sample mean equals the population mean
__B____21. Since it is better to let a guilty man go free than convict an innocent man in our legal system (innocent until proven guilty), which type of error is favored by the courts?
__B___22. If I form a sampling distribution of the mean from a bi-modal population, what shape will the distribution have?
__D___23. A drunk man fails a blood alcohol test. What type of error has been committed?
Part II (computational) Show work for partial credit!!!!
1. The mean number of hours slept per night in the population is μ = 7.7 with a standard deviation of σ = 1.5. A sample of N = 36 patients on anti-depressants were found to sleep an average of 
= 6.8 hours. Does being on anti-depressants change the number of hours slept? Set α =.05
1A. Is this a one or two tail test? (1 point)
1B. Perform a hypothesis test:
STEP 1: State the hypotheses in both words and symbols
(include and label both H0 and H1). (online users can use the “insert” option on the MS Word menu, then choose “symbol” for Greek characters). (4 points)
In Words:
H1: The number of hours slept by the population of patients on antidepressants differs from the number of hours slept by the general population
H0: The number of hours slept by the population of patients on antidepressants is no different from the number of hours slept by the general population
In Symbols:
H1: µantidepressant ≠ 7.7
H0: µantidepressant = 7.7
STEP 2: Set up the criteria for making a decision. That is, find the critical value.
(2 points)
Z Critical (α = 0.05, two-sided) = ±1.96
STEP 3: Summarize the data into the appropriate test-statistic. That is, compute the test statistic. (3 points)
Z = (
- µ)/ δ
δ= 1.5/ 6
δ= 0.25
Z = (6.8 – 7.7)/ 0.25
Z = -3.6
STEP 4: Evaluate the null hypothesis (Reject or Fail to reject?)
(1 point)
Reject the null hypothesis since the Z-statistic is more extreme than the critical value
STEP 5: What is the conclusion (i.e. interpret your results)? (1 point)
Conclude that the number of hours slept by the population of patients on antidepressants significantly differs from the number of hours slept by the general population
Based on your decision in Step 4 what type of error MIGHT you have made?
(1 point)
There is 5% likelihood that I made a Type I error by rejecting a null hypothesis that is actually true
2. The general population has an average resting heart rate of m = 80 b.p.m., with a standard deviation of 3.3. A sample of N = 30 people who exercise are found to have a heart rate average of 78 b.p.m. Do people who exercise have a slower (lower) heart rate?
Set a = .01.
2A. Is this a one-tail or two-tail test? A. (1 point)
a. one-tail
b. two-tail
Step 1: State the null and research hypothesis in words. Be sure to label H1 and H0! (2 points)
H1: The resting heart rate in the population of exercisers is slower than the resting heart rate in the general population
H0: The resting heart rate in the population of exercisers is equal to or higher than the resting heart rate in the general population
State the null and research hypothesis in symbols. Be sure to label H1 and H0! (2 points)
H1: µexercisers < 80
H1: µexercisers ≥ 80
Step 2: Find the critical value for the test. Be sure to use the proper sign for its value.
(2 points)
Z-Critical (α = 0.01, one-sided) = -2.33
Step 3: Compute the appropriate test statistic. (4 points)
Z = (
- µ)/ δ
δ= 3.3/ √30
δ= 0.6025
Z = (78 – 80)/ 0.6025
Z = -3.32
Step 4: What is your decision about the null (based on step 3 above)? (1 point)
Reject the null hypothesis as the Z statistic is more extreme than the critical value
Step 5. Interpret the results of the statistical test (in plain English). (1 point)
Based on the evidence provided by the sample, the resting heart rate in the population of exercisers is slower than the resting heart rate in the general population
2b. If you had rejected the null hypothesis in the above problem, what is the probability that you would have made a Type I error? (1 point)
P (Type I error) = 0.01
End of Exam……………………………………………………………
