Important Instructions: Throughout the exam, round to no less than four decimal
ID: 3050478 • Letter: I
Question
Important Instructions: Throughout the exam, round to no less than four decimal places on each step (e.g. 4.8765). Final answers may be rounded to no less than two decimal places (e.g. 3.65). Remember to show your work for all calculations! Following these instructions is critical to obtaining the correct answers and receiving full credit.
Computation (10 points)
You are a graduate student in psychology administering IQ tests to clients, using the Wechsler Adult Intelligence Scale (WAIS) as your chosen IQ test. You know that the population mean and standard deviation for the raw intelligence test scores are = 80 and = 13. As indicated in the manual, the developers of the test use a standardized distribution with a mean and standard deviation for the WAIS scores of = 100 and = 15. Each raw score is transformed into a standardized score to ease interpretation. For each client below, calculate the missing scores.
***Use the table below to record your answers. If additional space is need, attach your NEATLY ORGANIZED hand calculations to this sheet.
Name of client: Doug
Raw score: 75
z-score:____(.5pt)
Standard Score: ____(.5pt)
Name of client: Mercedes
Raw score:_______(.5pt)
z- score_____(.5pt)
Standard score: 115
What % of the distribution is expected to fall below a raw exam score of 90?
What % of the distribution is expected to fall below a standardized exam score of 90?
After testing all your clients, you find that their mean raw score is 82 (n = 150). What is the probability of selecting a random sample of n = 150 scores with a sample mean this large or larger?
Another graduate student told you she obtained a standardized score sample mean of 98 for her clients (n = 120). What is the probability of selecting a random sample of n = 120 scores with a sample mean this large or larger?
Hypothesis Testing (20 points)
You are a researcher interested in whether optimism is related to creativity. You have recruited a sample of local artists, writers, and musicians and identified some of them as “highly optimistic” according to an Optimism Scale. You want to find out whether those who are “highly optimistic” are rated as more creative, as compared to other artists who were not identified to be “highly optimistic. Higher scores on the creativity rating scale indicate higher creativity, and data drawn from the general population of local artists yielded a = 42 with =5. Creativity scores for the “highly optimistic” artists are listed below. Use the 6 steps of hypothesis testing to set up and determine the results of this study. You decide whether to conduct a one-tailed or two-tailed test and at what level to set alpha.
Use this answer sheet to NEATLY write your answers to the six steps.
45,44,43,46,47,45,48,46,48,43,45,46,47,49,47,45,44,49,47,44
Step #1: A priori expectations (1 pt)
Question of interest:
Prediction:
Step #2: Set up hypotheses (4 pts)
Step #3: Set criteria for decision (4 pts)
Alpha (1 pt) = zcritical value (1 pt) =
Decision rule (2 pts):
Step #4: Collect data/ compute statistic (Hint: include effect size) (5 pts)
Step #5: Make a decision-report results (Hint: Don’t forget to use standard format) (5 pts)
Step #6: Interpret the results (Hint: More than restating results; demonstrate you have thought critically about the results) (1 pt)
SPSS (20 points)
You are a health psychologist interested in the effects of healthcare accessibility. You have access to several years of data from a national repository of health statistics that includes Americans’ scores on a measure called the Barriers to Wellness Inventory (BWI). Higher scores indicate greater stress related to difficulty accessing healthcare. You want to know whether Americans are more or less stressed about barriers to accessing healthcare today than five years ago, according to the BWI. Data from spring 2012 indicates that Americans on average scored = 55 on the BWI. National data for fall 2017 is not yet available, so you have collected your own sample of n= 25 individuals to compare to the 2012 population mu. Use the 6 steps of hypothesis testing and SPSS to determine the results of this study. Use the SPSS dataset posted with the exam on Canvas. Conduct a one sample t-test (compare means) and answer the questions below. You decide whether to conduct a one-tailed or two-tailed test and at what level to set alpha. Record your answers on the answer sheet and attach SPSS output.
Step #1: A priori expectations (1 pt)
Question of interest:
Prediction:
Step #2: Set up hypotheses (4 pts)
Step #3: Set criteria for decision (4 pts)
Alpha (1 pt) = tcritical value (1 pt) =
Decision rule (2 pts):
Step #4: Collect data/ compute statistic (Hint: Include effect size) (5 pts)
Step #5: Make Decision-report results (5 pts)
Step #6: Interpret the results (Hint: This is more than restating the results; demonstrate that you have thought critically about the results) (1 pt)
Explanation / Answer
z-score = (raw score - 80)/13
standard score = 100 + z-score * 15
a)
Raw score: 75
z-score = (75 - 80)/13 = -0.384615
Standard Score: (100 -0.384615*15) = 94.2307692308
b)
Name of client: Mercedes
Raw score:_______(.5pt)
z- score_____(.5pt)
Standard score: 115
z-score = (115 - 100)/15 = 1
Raw score = 80 +1 *13 = 93
c)
P(Raw < 90)
= P(Z< ( 90 -80)/13)
= P (Z<0.77)=0.7794
d)
P(Standard < 90)
= P (Z<0.67)=0.2514
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