81 terms

# psy10

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A researcher is interested in the sleeping habits of American college students. A group of 50 students is
interviewed and the researcher finds that these students sleep an average of 6.7 hours per day. For this study,
the 50 students are an example of a(n)
sample
A researcher is curious about the average IQ of registered voters in the state of Florida. If this average could
be obtained, it would be an example of a
parameter
The relationship between a statistic and a sample is the same as the relationship between
parameter and population
After measuring two individuals, a researcher can say that the score for one individual is different than the
score for the other, but it is impossible to determine which score is larger or how much larger. What scale of
measurement is being used in this situation?
nominal
What is the value of EX - 1for the following scores?
Scores: 2, 4, 7
12
How would the following mathematical operation be expressed in summation notation? "Subtract 4 points
from each score, square the resulting value, then find the sum of the squared numbers.
E(X- 4)2
Although research questions usually concern a _____, the actual research is typically conducted with a _____.
population, sample
For the following frequency distribution, what is the value of E X?
X f
5 2
4 4
3 1
2 3
35
What kind of frequency distribution graph is appropriate for scores measured on an interval or ratio scale?
either a histogram or a polygon
A professor recorded scores from a 5-point quiz for each student in an introductory psychology class. If the
data are presented in a frequency distribution graph, what type of graph should be used?
a bar graph
Refer to the following table showing a frequency distribution of quiz scores.
X f
5 6
4 5
3 5
2 3
1 2
How many individuals had a score of X = 2?
3
For the following distribution, what is the highest score?
X f
20-25 2
15-19 5
10-14 4
5-9 1
cannot be determined
For the following distribution, how many people had scores greater than X = 14?
X f
20-25 2
15-19 5
10-14 4
5-9
7
For the following data, N = _____.
X f
4 2
3 4
2 3
1 2
11
What is the mean for the following sample of scores?
Scores: 1, 2, 5, 4
3
A population of N = 10 scores has a mean of U = 80. If 5 points are added to every score in the distribution,
what is the value of the new mean?
U = 85
A sample has a mean of M = 25. If one person with a score of X = 25 is added to the sample, what effect will
it have on the sample mean?
The sample mean will remain the same
One sample of n = 4 scores has a mean of M = 10, and a second sample of n = 8 scores has a mean of M = 20.
If the two samples are combined, the mean for the combined sample will be
greater than 15 but less than 20
What is the mean for the population of scores shown in the frequency distribution table?
X f
5 1
4 2
3 3
2 4
1 2
32/12 = 2.67
What is the median for the population of scores shown in the frequency distribution table?
X f
5 1
4 2
3 3
2 4
1 2
2.5
A teacher gave a reading test to a class of 5th-grade students and computed the mean, median, and mode for
the test scores. Which of the following statements cannot be an accurate description of the scores?
No one had a score exactly equal to the mode.
The sum of the squared deviation scores is SS = 60 for a population of N = 5 scores. What is the variance for
this population?
60/5 = 12
The variability of the scores in a sample tends to be _____ the variability of the scores in the population from
which the sample was obtained.
smaller than
Which of the following samples would have the largest value for sample variance?
All the samples would have exactly the same variance.
On an exam with a mean of average = 70, you have a score of X = 65. Which of the following values for the
standard deviation would give you the highest position within the class?
standard deviantion = 0
Without doing any serious calculations, which of the following samples has the largest variance?
1, 5, 8, 12, 22
For a population with mean = 80 and stdev = 10, what is the z-score corresponding to
X = 95?
+1.50
For a population with mean = 100 and X = 20, what is the X value corresponding to z = -0.50?
90
For a population with stdev = 10, a score of X = 60 corresponds to z = -1.50. What is the population mean?
75
A population with mean = 85 and stdev = 12 is transformed into z-scores. After the transformation, what are the
values for the mean and standard deviation for the population of z-scores?
mean = 0 and stdev = 1
Last week Tom had exams in Statistics and in English. He scored 10 points above the mean on both exams.
From this information, what can you can conclude about the z-scores for Tom's two scores?
Both of Tom's z-scores are positive.
A sample has M = 72 and s = 4. In this sample, what is the X value corresponding to z = -2.00?
X = 64
You have a score of X = 65 on an exam. Which set of parameters would give you the best grade on the exam?
mean = 60 and stdev = 5
For a sample with M = 50 and s = 12, what is the X value corresponding to z = -0.25?
47
For a population with stdev = 10, a score of X = 60 corresponds to z = -1.50. What is the population mean?
75
For a sample with M = 80, a score of X = 88 corresponds to z = 2.00. What is the sample standard deviation?
4
Which of the following is an advantage of transforming X values into z-scores
None of the other options is an advantage.
A vertical line is drawn through a normal distribution at z = -1.00. The line separates the distribution into two
sections. What proportion of the distribution is in the larger section?
84.13%
What proportion of a normal distribution corresponds to z-scores greater than +1.04?
0.1492
What proportion of a normal distribution is located between z = 1.00 and z = 1.50?
0.0919
For any normal distribution, the percentile rank for z = 0.50 is
69.15%
A distribution is normal and has average = 90 and stdev = 10. What is the 64th percentile?
93.6
A true/false test has 36 questions. Using the normal approximation to the binomial distribution, the
probability of getting more than 25 correct by just guessing can be computed as
p(X greater than 25.5)
A jar contains 40 red marbles, 20 blue marbles, and 10 black marbles. If you take a random sample of n = 3
marbles from this jar, and the first two marbles are both red, what is the probability that the third marble will
be black?
10/68
For any normal distribution, what are the z-score values that form the boundaries for the middle 80%?
z = plus or minus1.28
The distribution of sample means (for a specific sample size) consists of _____
the sample means for all the possible samples (for the specific sample size)
The symbol that corresponds to the standard error of M is _____.
stdev M
A random sample of n = 36 scores is selected from a population. Which of the following distributions
definitely will be normal?
The distribution of sample means will form a normal distribution.
When a random sample is selected from a population, the sample mean is not expected to be exactly equal to
the population mean. On average, the size of the difference between a sample mean and the population mean
is predicted by _____.
the standard error
Samples of size n = 4 are selected from a population with m = 80 with stdev = 8. What is the standard error for
the distribution of sample means?
4
A sample of n = 25 scores is determined to have a standard error of 2 points. What is the standard deviation
for the population from which the sample was obtained?
10
If a sample of n = 4 scores is obtained from a population with m = 70 and stdev = 12, then a sample mean of M =
76 would correspond to a z-score of _____.
z = 1.00
A random sample of n = 4 scores is obtained from a population with stdev = 10. If the sample mean is 10 points
greater than the population mean, what is the z-score for the sample mean?
+1.0
For a particular population a sample of n = 4 scores has an expected value of 10. For the same population, a
sample of n = 16 scores would have an expected value of _____.
10
A sample of n = 4 scores has a standard error of 12. What is the standard deviation of the population from
which the sample was obtained?
24
A random sample of n = 4 scores is obtained from a normal population with mean = 40 and stdev = 6. What is the
probability of obtaining a mean greater than M = 46 for this sample?
0.1587
A sample is obtained from a population with mean = 100 and stdev = 20. Which of the following samples would
produce the z-score closest to zero?
a sample of n = 25 scores with M = 102
A sample of n = 4 scores has a standard error of 10 points. For the same population, what is the standard error
for a sample of n = 16 scores?
5
A random sample of n = 4 scores is obtained from a population with a mean of mean = 80 and a standard
deviation of stdev = 10. If the sample mean is M = 90, what is the z-score for the sample mean?
z = 1.00
For a normal population with a mean of mean = 80 and a standard deviation of stdev = 10, what is the probability of
obtaining a sample mean greater than M = 75 for a sample of n = 25 scores?
p = 0.9938
A z-score that is used for hypothesis testing is also called a _____.
test statistic
The numerator of the z-score test statistic measures _____.
the actual distance between M and U(mean)
Even if a treatment has no effect it is still possible to obtain an extreme sample mean that is very different
from the population mean. If this happens, you are likely to _____.
reject H0 and make a Type I error.
Which combination of factors will increase the chances of rejecting the null hypothesis?
a small standard error and a large alpha leve
A researcher uses a hypothesis test to evaluate H0 mean = 80. Which combination of factors is most likely to
result in rejecting the null hypothesis?
M = 90 and n = 20
A researcher uses a hypothesis test to evaluate H0 mean = 80. If the researcher obtains a sample mean of M = 88,
which combination of factors is most likely to result in rejecting the null hypothesis?
stdev = 5 and a = .05
A researcher is predicting that a treatment will increase scores. If this treatment is evaluated using a
directional hypothesis test, then the critical region for the test _____.
would be entirely in the right-hand tail of the distribution
A sample of n = 25 individuals is selected from a population with mean = 60 and stdev = 10 and a treatment is
administered to the sample. After treatment, the sample mean is M = 63. What is the value of Cohen's d for
this sample?
0.30
The power of a hypothesis test is defined as
the probability that the test will reject H0 if there is a real treatment effect.
If a researcher reports a t statistic with df = 20, how many individuals were in the sample?
n = 21
If a sample consists of n = 15 individuals, then what is the df value for the t statistic?
14
A researcher reports t(24) = 5.30 for an independent-measures experiment. How many individuals
participated in the entire experiment?
26
One sample of n = 5 scores has a variance of s^2= 10 and a second sample of n = 10 scores has s^2= 20. If the
pooled variance is computed for these two samples, then the value obtained will be _____.
closer to 20 than to 10
One sample has a variance of s^2 = 20 and a second sample has a variance of s^2 = 30. If the two samples are the
same size, what is pooled variance for the two samples?
somewhere between 20 and 30 but it is impossible to determine exactly where
In an independent-measures hypothesis test, if t = 0, then _____.
the two sample means must be equal
An independent-measures research study with n = 6 subjects in each treatment has SS = 70 for treatment 1
and SS = 50 for treatment 2. For these data, the estimated standard error for sample mean differences equals
.
2
In general, if the variance of the difference scores increases, then the value of the t statistic will _____.
decrease (move toward 0 at the center of the distribution)
A researcher uses a repeated-measures study to compare two treatment conditions with a set of 20 scores in
each treatment. What would be the value of df for the repeated-measures t statistic?
df = 19
A repeated-measures study produces a sample mean difference of MD = 4.5 with s^2
= 100 for a sample of n =
16 participants. For this study, the estimated value of Cohen's d would be _____
d = 4.5/10 = 0.45
The following data were obtained from a repeated-measures research study. What is the value for MD?
Subject 1st 2nd
#1 8 10
#2 6 12
#3 10 7
#4 9 11
#5 7 10
MD = 2
A sample of difference scores has a mean of MD = 5. Which combination of factors is most likely to produce
a significant difference?
n = 9 with a variance of s^2
= 36 for the difference scores