Q1
Which of the following is an assumption underlying the independent groups t-test?
Answer
the sampling distribution of the mean should be normal
the scores in one sample should be dependent on the scores in the other sample
the sampling distribution of the differences between means should be normal
the variance in one sample should be four times the variance in the other sample
Q2
Which of the following terms best describes the sentence: ‘In a blind-tasting, people will
not be able to tell the difference between margarine and butter’
Answer
a directional hypothesis
an operational definition
a null hypothesis
a non-directional hypothesis
Q3
Given a normal sampling distribution of means with a mean of 150, which of the following
is the standard deviation for the corresponding raw score population
Answer
1
150 divided by the square root of the sample N
150
the standard error multiplied by the squareroot of sample N
Q4
A researcher was interested in stress levels of lecturers during lectures. She took the same
group of 8 lecturers and measured their anxiety (out of 15) during a normal lecture and
again in a lecture in which she had paid students to be disruptive and misbehave. She
found a mean difference in lecturer anxiety between the two lectures was 6.25 with a
standard deviation of difference scores of 4.80. The researcher concluded that:
Answer
Can' t tell from the information given
Anxiety levels were significantly different in lectures in which students misbehaved
compared with normal lectures
Anxiety levels were significantly higher in lectures in which students misbehaved
There were no significant differences between anxiety levels in normal lectures and
in those in which students misbehaved.
Q5
A variable manipulated by a researcher is known as:
Answer
a predictor variable
a dependent variable
a confounding variable
an independent variable
Q6
What does effect size show?
Answer
How big a sample the study needs
How much power a study has
How large a relationship or difference is
How significant a result is
Q7
A z-test is the ratio of:
Answer
The difference between a sample and a population divided by the difference that
usually occurs by chance within the sample
The difference between two samples divided by the difference that usually occurs by
chance between two samples
The difference between a sample and a population divided by the difference that
usually occurs by chance between a sample and the population
The association between a sample and a population divided by the association that
usually occurs by chance between a sample and the population
Q8
The critical region for a hypothesis test consists of
Answer
outcomes have a very high probability if the null hypothesis is true
outcomes that have a very low probability if the null hypothesis is true
outcomes that have a very high probability whether or not the null hypothesis is true
outcomes that have a very low probability whether or not the null hypothesis is true
Q9
A null hypothesis:
Answer
states that the experimental treatment will have an effect
is rarely used in experiments
predicts that the experimental treatment will have no effect
is what we use when we are not sure what effect we might find
Q10
An independent- groups experiment uses one sample with n= 6 and a second sample with
n= 10 to compare two experimental treatments. The t statistic from this experiment will
have degrees of freedom equal to ________.
Answer
15
8
7
14
Q11
What is p the probability of?
Answer
that the results are not due to chance, the probability that the null hypothesis is false
observing results as extreme (or more) as observed, if the null hypothesis is true
that the results are due to chance, the probability that the null hypothesis is true
that the results would be replicated if the experiment was conducted a second time
Q12
The results of a hypothesis test are reported as follows: z(29) = 2.70, p < .05. Based on this
report, how many individuals were in the sample?
Answer
28
30
29
Cannot be determined from the information provided
Q13
Setting the p value at 0.1 instead of 0.05 increases the chances of
Answer
Making a Type I error
Making a Type II error
decreasing power
Increasing the effect
Question 14
Which of these statements about statistical power is false
Answer
Power is the ability to detect an effect
Power is linked to the probability of making a type I error
Power tells us how clinically meaningful our results are
we can use power to determine how big a sample is required to detect an effect
of a certain size
Q15
The repeated measures t-test is
Answer
requires the assumption that differences between paired observations follow a normal
distribution
suitable for very small samples
impractical for large samples
equivalent to a chi-squared test
Q16.
A researcher wished to demonstrate the effectiveness of a new drug in enhancing
memory in nursing home residents. The average memory score for residents before
the treatment is 11.9, with a standard deviation of 3.2. The researcher anticipates
that after the program the average memory score will be around 13.5.
(a) What is the effect size (d)?
(b) What is the numeric value of the noncentrality parameter with a sample of 16?
(c) What is the statistical effect (delta) with a sample of 16?
(d) How much power did the researcher have with a sample of 16?
(e) How many people would he need to obtain power = .85?
(use whole
numbers)
(f) What would power be if the standard deviation was 4.5 for the sample of 16?
Q17.
A clinical psychologist wanted to assess the impact of the Brisbane floods on the
anxiety level of local children. He assessed 36 children from St Lucia on a measure of
childhood anxiety. Fortunately, he had used this measure in a previous study using
other children from St Lucia prior to the floods. The mean score on the measure in
the pre-flood sample of 3.87. The mean for the post-flood sample was 4.89 with a
variance of 6.81.
Calculate the appropriate statistic to evaluate whether the flood had effected the
mean level of anxiety in local children. Use this information to fill in the blanks:
A
t-test showed that anxiety in local children after the flood was
than the anxiety found before the flood, t (
than .05. The statistical null
)=
, p is
Q18.
A research team were interested in the effect of paternal smoking on the cognitive
development of their offspring. They wish to compare 1 year old infants who either had a
father who smoked during their gestation or fathers who did not. Based on previous similar
studies they expect to find children of smoking fathers to have a mean score of 25 on a
measure of infant cognitive functioning and the children of non-smokers to have a mean
score of 30 with a standard deviation of 8. The researchers plan to run their study with 20
children in each group. Using this information complete the following questions by filling
in the blanks.
(a) What is the expected effect size (d)?
(b) What is the statistical effect (delta)?
(c) How much power do the research team have for this sample of 20 children in each
group?
(d) How much power would they have if they were able to recruit 30 children in each
group?
(e) How many children would they need to recruit into the study to obtain power = .80
(report in whole numbers)
(f) What would power be if there was standard deviation of 4 for the sample of 20 children?
Q19.
A researcher is interested in the effectiveness of a new anti-anxiety drug on avoidance
behaviour. She tests the effectiveness of the drug on avoidant behaviour in a sample of 90
rodents using a standardised task with a known mean response time of 5.8 seconds and a
standard deviation of 2 seconds. In the sample given the drug she finds a mean avoidance
response time of 4.8 seconds and a standard deviation of 1.5 seconds.
Calculate the appropriate statistic to evaluate whether the avoidance response time for the
rodents given the new drug is significantly different from the mean avoidance response
time usually found on the task. Use this information to fill in the blanks:
A single-sample
test showed that the avoidance response time for the rodents
given the new drug was
on the task,
than the known mean avoidance response time found
=
hypothesis would state that mu =
, p is
than .05. The statistical null
.
Q20.
Two sleeping tablets (Drugs A and B) were tested on a sample of 8 insomniacs. Each
insomniac received drug A for one week of the study, and drug B for the other week
(assume that the order in which the insomniacs took the two drugs was
counterbalanced).
The total amount of time (in minutes) spent lying awake before falling asleep was
recorded for each subject for each week, yielding the following data:
Drug A: 29 31 33 26 22 27 23 20
Drug B: 28 27 34 25 21 23 20 16
Compute the appropriate statistic to determine whether there is a difference in the
effectiveness of the two drugs. Use this information to fill in the blanks:
A
t-test revealed that the time insomniacs spent lying awake before falling
asleep was
after taking Drug A than Drug B, t(
than.05.Therefore we
the null hypothesis.
)=
, p is