PSY230 Cumulative Quiz (CH 1-9)
The conventional levels of significance in hypothesis testing in psychology are
.01 and .05
Which of the following is an example of a standard LARGE effect size?
.8
In a distribution of Z scores, the mean is always
0
In a distribution of Z scores, the mean z-score is always
0
Using a normal curve table, if a person received a test score that is in the top 16% of all test scores, the person's Z score must be at least
1
Based on the following scores: 3, 4, 6, 7, 10, 10, 30 What is the mode?
10
A school psychologist is using a depression inventory—on which a score of 0 indicates no depression and a score of 10 indicates severe depression—to see if the level of depression in fourth graders in a particular class of 20 students differs from that of fourth graders in general at a school. The results of previous testing indicate that fourth graders at the school usually have a score of 5 on the scale, but the variation is unknown. The current sample of 20 fifth graders has a mean depression score of 4.4. If the unbiased estimate of the population's variance is 15, the variance of the distribution of means is
15 / 20 = 0.75
In a small private college, 80 students play baseball, 70 students play football, 50 students play basketball, and 550 students do not play any sport. If a student is approached at random, what is the probability that he/she will play baseball or football?
150 / 750 = .20
If the standard deviation is 4, the variance is
16
For the following scores: 8, 2, 6, 0, 5, 0, 0 What is the median?
2
If the mean of a test is 14 and its standard deviation is 2, the Z score for a person with a raw score of 18 is
2
If a sample includes 27 people, the degrees of freedom used in the formula to estimate the population variance would be
26
If the variance is 9, than the standard deviation is:
3
Your sample of 12 people is being compared to a known population with a mean of 200 and a variance of 36. What is the variance of the distribution of means?
3.00
Using the percentage approximations for the normal curve, the percentage of scores between the mean and one standard deviation below the mean is
34%
In a normal curve, what is the percentage that falls between a z-score of -1 and a z-score of +2?
34%+34%+14% = 82%
Based on the scores: 1, 9, 3, 6, 1, 2, 6, 2, 2, 8 What is the mean?
4
If a researcher says that he is choosing cutoffs at .05 for his one-tailed test, that means that he will reject the null hypothesis only if his sample mean falls in the top _____ of his distribution.
5%
If sample A includes 34 people, and sample B includes 32 people, the total degrees of freedom would be
64
If you have a standard deviation of 9, what will your variance be?
81
Frequency tables and histograms are oftentimes show in published research articles because of their importance.
False
In a sample of three people, the first person has a score 5 points above the mean, and the second person has a score 3 points above the mean. Which of the following provides the most accurate description of the score for the third person?
It is below the mean by 8 points.
In a sample of four people, Person A has a score 5 points below the mean, Person B has a score 3 points above the mean, and Person C has a score 2 points above the mean. Which of the following provides the most accurate description of the score for Person D?
It is equal to the mean
What is the value of putting numbers in a frequency table?
It makes the pattern of numbers clear at a glance.
Which of the following student characteristics is an example of a nominal variable:
Nationality (U.S., Japanese...)
A health psychologist is interested in the effectiveness of a new exercise on reducing the rate of heart attacks because the exercise requires no equipment and, therefore, can be done without cost. What is the research (or alternative) hypothesis?
The exercise will reduce the rate of heart attacks.
How would a psychologist test the hypothesis that a new stress-reduction program really works?
Try to reject the hypothesis that it does not work.
Rejecting the null hypothesis when the null hypothesis was true (aka the research hypothesis is false) is
a Type I error.
A histogram looks like
a city skyline.
A psychologist who constructs a frequency table to summarize data collected on the amount of stress people have experienced in the last 2.5 weeks is using
a descriptive statistical method.
A one-tailed test is associated with
a directional hypothesis.
If a psychologist rating empathetic responses of participants to strangers' distress on a scale of 1 to 20 find that most participants have ratings of either 8 or 16, the distribution of ratings is:
bimodal.
The length of time a person talks in a group discussion is an example of a(n):
continuous variable.
The two types of statistical methods we discussed in class are:
descriptive and inferential.
Some psychologists have argued that simple significance tests are misleading, and that a better statistic to evaluate the outcome of an experiment would be the
effect size.
A school psychologist is using a depression inventory--on which a score of 0 indicates no depression and a score of 10 indicates severe depression--to see if the level of depression in fourth graders in a particular class of 20 students differs from that of fourth graders in general at a school. The results of the previous testing indicate that fourth graders at the school usually have a score of 5 on the scale, but the variation is unknown. The current sample of 20 fourth graders has a mean depression score of 4.4. The psychologists tests the null hypothesis that the level of depression of fourth graders in this class does not differ from fourth graders in general at the school and obtains a t score of -0.20. The decision regarding the null hypothesis would be to
fail to reject it.
If the cutoff Z score on the comparison distribution is 1.64 and the sample Z score is 1.32 on the comparison distribution, the correct decision is to
fail to reject the null hypothesis
A student wants to study the effect of stress on memory in students at his college. He recruits participants by posting a sign-up sheet for anyone willing to participate, the student is conducting:
haphazard selection.
The fact that probabilities are proportions (think of a p-value) means that they
have to range from 0 to one.
Power is the probability that
if the research hypothesis is true, the experiment will support it.
The reason why someone might put numbers into a frequency table is because it's helpful in that
it makes the pattern of numbers clear at a glance.
Typically, the __________ the effect size, the more power a finding has.
larger
The most common measures of central tendency and variability reported in research articles are
mean and standard deviation.
The middle value in a set of scores arranged from lowest to highest is the
median.
The statistical method currently used to combine the results of multiple studies is
meta-analysis.
The mean and the mode for a statistics test will be the same if the distribution is
normal
The mean and the mode for a statistics test will be the same if the distribution is
normal.
A psychologist who states that there will be no difference between a new approach to therapy and the standard approach is stating a
null hypothesis
Which of the following would usually be considered "marginally significant"?
p between .05 and .10
If a student who wants to study alcohol use at a high school obtains a complete list of the students and has a unbiased computer program select as many people as needed for the study, the student is conducting
random selection.
A number of patients are all rated for their degree of depression. If one patient is rated as an 8 on a 20-point scale, 8 represents that particular patient's:
score.
A psychologist conducts a study and finds that d = .13 This effect size would most likely be described as
small
The variance of a distribution of means
smaller than the original population variance.
A normal curve is:
symmetrical (not skewed to the left or right).
A "normal" curve is:
symmetrical.
Your professor asks you to update a manuscript with the results of a t test for dependent means and provides you with the following information: there were 19 people in the study, the t score was 4.36, and the result was significant at the .01 level. The best way to present this information would be
t (18) = 4.36, p<.01
An experimenter hypothesizes that biology majors score higher than literature majors on an intelligence test. If the mean score for biology majors was 18.8 and the mean score for literature majors was 21.3, and the Sdifference was 0.9, the t score was
t = (18.8 - 21.3) / 0.9 = -2.78
The main difference between a Z score and a t score is that
t scores are used when the population variance is unknown.
A t test for dependent means would be used to compare
the level of reading comprehension of the same students at the beginning and at the end of a speed-reading class.
A frequency table lists
the number of scores at each value.
The alpha level is
the probability of a Type I error.
If a t test for dependent means is reported in a research article as "t (38) = 3.11, p < .01," then
the result is significant
The mean of a distribution of means is
the same as the original population mean.
A result is considered statistically significant when
the sample score is so extreme that the null hypothesis is rejected.
When using a t table, the degrees of freedom used for a t test for independent means is
the sum of the degrees of freedom for the two samples.
The correct description of the mean is
the sum of the scores divided by the number of scores.
Psychologists use frequency tables and histograms to show:
the way the numbers they collected are distributed.
When a psychologists rejects the null hypothesis at the .05 level, the results of a study indicate that
there is less than a 5% chance of getting such an extreme result if the null hypothesis is true.
Rejecting the null hypothesis at the .05 level means that
there is less than a 5% chance of getting such an extreme results if the null hypothesis is true.
One important advantage of using effect sizes is that
they are standardized scores that make comparisons of different studies easier.
A psychologist is studying aggressive tendencies in people. She develops and inventory to measure aggression on a 10-point scale. In this example, aggression is being measured and is therefore a(n):
variable.