Psy 550 Final
• For each of the following examples, explain whether the researcher has made a correct decision or has made a Type 1 or Type 2 error. Explain why.
1. Dr. G rejects the null hypothesis although the independent variable had no effect.
2. Dr. R rejects the null hypothesis when it ...
Psy 550 Final
•
For each of the following examples, explain whether the researcher has
made a correct decision or has made a Type 1 or Type 2 error. Explain
why.
1. Dr. G rejects the null hypothesis although the independent variable
had no effect.
2. Dr. R rejects the null hypothesis when it is false.
3. Although the independent variable had an effect, Dr. E does not reject
the null hypothesis
Your
Answer: 1. Type I error is made when we reject the null hypothesis, but the null hypothesis is
actually true. Our decision is that the population means are not equal when they
actually are equal- rejecting something that is true.
2. This would be a valid choice as Dr. R is rejecting a hypothesis that is false.
3. A Type II error occurs when the null hypothesis is accepted although in the
population the research hypothesis is true. The population means are not equal,
but the results of the experiment do not lead to a decision to reject the null
hypothesis – failing to reject something that is false
•
Question Points: 16..0
• 2
Explain the value of reversal designs (ABA designs) in single-case research.
Your Answer:
According to Privitera (2020), reversal designs are usually conducted in applied areas of research in
order to investigate solutions that can be beneficial to either individuals or our society. One advantage
is that the design can be used to apply treatments that benefit participants. In a reversal design (ABA
design), a single participant is observed prior to (A), during (B), and after (A) a manipulation or
treatment (p. 257-258)
A (baseline phase) --> B (treatment phase) --> A (baseline phase)
•
Question Points: 10..0
• 3
Explain how a one-way analysis of variance works. How do you use between-
and within-group variability?
Your Answer:
One-way analysis of variance (one-way ANOVA) looks at the differences between the mean of 2 or
more samples. Between-group variability looks at the variations caused by differences between
different groups. Within-groups variability looks at variations caused by differences within each
individual group, differences not caused by the independent variable.
•
Question Points: 10..0
, •4
After watching nursery-school children, Ken Garoo wants to test the
hypothesis that some toys are more fun to play with than others. He
decides to compare “fun” toys (blocks) with “unfun” toys (stuffed animals).
He also wishes to see if there is a sex difference, as well, so sex is added as
an independent variable. A) What kind of design is needed? B) Diagram it
out. C) Assuming 20 subjects are needed per cell, how many subjects are
needed for this study?
Your Answer:
a) The type of design would be a 2x2 factorial design as it will test the factors within one sample.
b)
Males Females
Fun Toys (blocks)20 20
Un-Fun Toys (stuffed 20 20
animals)
c) 80 subjects would be needed if there are 20 subjects per cell as visualized above (20x4 = 80)
•
Question Points: 16..0
•5
Bill Board is “lording” his SAT score over his friend, Rhoda Dendron, who took
the ACT. “You only got a 25 in math,” he chortled, “while I got a 300 in
math.” Given that the SAT has a μ of 500 and a σ of 100, and the ACT has a μ
of 20 and a σ of 5, what is wrong with Bill’s logic (give the answer in both z
scores and percentile ranks).
Your Answer:
Bill is incorrect to “lord” his SAT score because the SAT and the ACT use different scoring methods.
z-score:
z = x – μ / SD
Bill’s z-score is 300- = -2
Rhoda’s z-score is 25- =
1 Percentiles:
SAT Math: 300/800 = 37.5%
ACT Math: 25/36 = 69% (36 is the highest you can score in ACT Math)
Bill’s z-score of -2 puts him below Rhoda’s z-score of 1 as she is closer to average than he is.
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