Exam Review (EDP 371)
A sample of n = 16 individuals is selected from a population with μ = 60 and σ = 6 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? 2.00 0.50 0.33 3.00
0.50
A normal distribution has a mean of µ = 70 with σ = 12. If one score is randomly selected from this distribution, what is the probability that the score will be less than X = 76? 0.3830 0.3085 0.1915 0.6915
0.6915
What is the mode for the following sample of n = 8 scores? Scores: 0, 1, 1, 1, 2, 2, 3, 3 3 13/8 = 1.625 1.5 1
1
For a particular population a sampling distribution of n = 4 scores has a mean value of 10. For the same population, a sampling distribution of n = 25 scores would have a mean value of ____. 4 20 10 8
10
What is the total number of scores for the distribution shown in the following table? X f 4 3 3 5 2 4 1 2 10 4 37 14
14
For the following discrete distribution of quiz scores, if a score of X = 3 or higher is needed for a passing grade, how many individuals passed? X f 5 6 4 5 3 5 2 3 1 2 3 21 16 11
16
A sample of n = 9 scores has a standard error of 6. What is the standard deviation of the population from which the sample was obtained? 18 6 2 54
18
If random samples, each with n = 4 scores, are selected from a normal population with µ = 80 and σ = 36, then what is the standard error for the distribution of sample means? 18 36 9 4
18
A skewed distribution typically has ____ tail(s) and a normal distribution has ____ tail(s). 2; 2 2,;1 1; 1 1; 2
1;2
What is the value of ΣX2 for the following scores? Scores: 1, 0, 2, 4 21 28 49 14
21
What is the value of SS (sum of squared deviations) for the following set of scores? Scores: 8, 3, 1 144 29 26 74
26
A population of N = 6 scores has ΣX = 12 and ΣX2 = 54. What is the value of SS for this population? 30 54 9 5
30
For a bell-shaped distribution with µ = 30, what is the most probable value for the mode? greater than 30 30 less than 30 0
30
For a sample with M = 80, a score of X = 88 corresponds to z = 2.00. What is the sample standard deviation? 4 8 16 2
4
The sum of the squared deviation scores is SS = 20 for a population of N = 5 scores. What is the variance for this population? 4 80 100 5
4
What is the value of Σ(X - 2) for the following scores? Scores: 2, 3, 5 8 6 10 4
4
What is the value of (ΣX)2 for the following scores? Scores: 1, 0, 2, 4 14 49 28 21
49
What is the mean for the following sample of scores? Scores: 1, 4, 5, 10 20 10 5 4
5
Samples of size n = 9 are selected from a population with μ = 80 with σ = 18. What is the standard error for the distribution of sample means? 6 80 2 18
6
Which combination of factors will produce the smallest value for the standard error? A large sample and a large standard deviation A large sample and a small standard deviation A small sample and a large standard deviation A small sample and a small standard deviatio
A large sample and a small standard deviation
What is the first step to be performed in the following mathematical expression? (ΣX)2 Add the squared scores. Add the scores. Square each score. Square the sum of the scores.
Add the scores
A group of quiz scores ranges from 3 to 10, but no student had a score of X = 5. If the scores are put in a frequency distribution table, X = 5 would not be listed in the X column. True False
False
A population with μ = 45 and s = 8 is standardized to create a new distribution with μ = 100 and s = 20. In this transformation, a score of X = 41 from the original distribution will be transformed into a score of X = 110. True False
False
A population with μ = 59 and s = 8 is standardized to create a new distribution with μ = 100 and s = 20. After the transformation, an individual receives a new score of X = 90. The original score for this individual was X = 51. True False
False
A researcher administers a treatment to a sample from a population with a mean of m = 60. If the treatment is expected to increase scores and a one-tailed test is used to evaluate the treatment effect, then the null hypothesis states that m > 60. True False
False
A sample of n = 25 scores is selected from a population with μ = 70 and σ = 20. It is very unlikely that the sample mean will be smaller than 72. True False
False
A set of scores ranges from X = 18 to X= 91. If the scores are put in a grouped frequency distribution table with an interval width of 10 points, the top interval would be 91-100. True False
False
For a normal distribution, proportions in the right-hand tail are positive and proportions in the left-hand tail are negative. True False
False
For a population with µ = 70 and σ = 5, about 95% of the individuals will have scores between X = 65 and X = 75. True False
False
If a set of exam scores forms a negatively skewed distribution, it suggests that the majority of the students did not score well on the exam. True False
False
It is impossible for the value of the mode to be greater than the value of the mean. True False
False
Multiplying every score in a sample by 3 will not change the value of the standard deviation. True False
False
T or F: For the distribution in the following table, the 80th percentile is X = 24. X c% 25-29 100% 20-24 80% 15-19 20%
False
T or F: For the distribution in the following table, the 90th percentile is X = 27.5. X c% 25-29 100% 20-24 80% 15-19 20%
False
T or F: In an experimental study, individuals in a control condition receive the experimental treatment.
False
T or F: The first step in computing Σ(X + 1) is to sum the scores.
False
T or F: The scores for a very easy exam would probably form a positively skewed distribution.
False
The average score for a population is an example of a statistic.
False
The mean is considered to be the "balance point" for a distribution because exactly half of the scores are located above the mean and exactly half are below the mean. True False
False
You can reduce the risk of a Type I error by using a larger sample. True False
False
What happens to the standard error of M as sample size increases? It stays constant. The standard error does not change in a predictable manner when sample size increases. It decreases. It also increases.
It decreases
A researcher is testing the effectiveness of a new herbal supplement that claims to improve physical fitness. A sample of n = 16 college students is obtained and each student takes the supplement daily for six weeks. At the end of the 6-week period, each student is given a standardized fitness test and the average score for the sample is M = 39. For the general population of college students, the distribution of test scores is normal with a mean of µ = 35 and a standard deviation of σ = 12. Do students taking the supplement have significantly better fitness scores? Use a one-tailed test with α = .05. Yes No
No
In a sample of n = 6 scores, the smallest score is X = 3, the largest score is X = 10, and the mean is M = 6. If the largest score is changed from X = 10 to X = 22, then what is the value of the new mean? The mean is M = 8. The mean is M=10. The mean is still M = 6. The mean is M = 7.
The mean is M = 8.
A Type I error occurs when a researcher concludes that a treatment has an effect but, in fact, the treatment has no effect. True False
True
A distribution of scores has a mean of 50, a median of 53, and a mode of 56. Based on this information it appears that the distribution is negatively skewed. True False
True
A mathematical proposition known as the central limit theorem provides a precise description of the distribution that would be obtained if you selected every possible sample, calculated every sample mean, and constructed the distribution of the sample mean. True False
True
A population of N = 5 scores has SS = 20 and σ2 = 4. If the 5 scores were a sample, the value of SS would still be 20 but the variance would be s2 = 5. True False
True
A population with SS = 90 and a variance of 9 has N = 10 scores. True False
True
A sample of n = 25 scores is selected from a population with a mean of µ = 80 and a standard deviation of σ = 20. The expected value for the sample mean (that is, the mean of the sampling distribution of means) is 80. True False
True
A sample of n = 9 scores is selected from a normal population with a mean of µ = 80 and a standard deviation of s = 12. The probability that the sample mean will be greater than M = 86 is equal to the probability of obtaining a z-score greater than z = 1.50. True False
True
After a researcher multiplies every score in a sample by 2, the standard deviation is found to be s = 10. The original sample had a standard deviation of s = 5. True False
True
For a normal distribution with µ = 80 and σ = 10 the score that separates the bottom 10% of the distribution from the rest is 67.2. True False
True
For a population of exam scores, a score of X = 83 corresponds to z = +0.50 and a score of X = 89 corresponds to z = +1.50. The population mean is μ = 80. True False
True
For a sample with a standard deviation of s = 10, a score with a deviation of +5 will have a z-score of z = 0.50. True False
True
For a set of scores measured on an ordinal scale, the median is the preferred measure of central tendency. True False
True
If the research prediction is that the treatment will decrease scores, then the critical region for a directional test will be in the left-hand tail. True False
True
If the sample data are in the critical region with α = .01, then the same sample data would still be in the critical region if α were changed to .05. True False
True
If the scores in a population range from a low of X = 5 to a high of X = 14, then the population standard deviation must be less than 15. True False
True
Most researchers would like the hypothesis test to reject the null hypothesis. True False
True
Standardized scores are "simple" values for the mean and standard deviation that do not change any individual's location within the distribution. True False
True
T or F: A correlational study is used to examine the relationship between two variables but cannot determine whether it is a cause-and-effect relationship.
True
T or F: A correlational study typically uses only one group of participants but measures two different variables (two scores) for each individual.
True
T or F: For the distribution in the following table, the percentile rank for X = 25 is 82%. X c% 25-29 100% 20-24 80% 15-19 20%
True
T or F: For the following scores, ΣX2 = 35. Scores: 1, 3, 5
True
T or F: If a researcher measures two individuals on a nominal scale, it is impossible to determine which individual has the larger score.
True
The range is usually considered to be a relatively crude measure of variability. True False
True
To calculate the variance for a population, SS is divided by N. True False
True
A distribution with µ = 55 and s = 6 is being standardized so that the new mean and standard deviation will be µ = 50 and s = 10. When the distribution is standardized, what value will be obtained for a score of X = 58 from the original distribution? X = 61 X = 55 X = 53 X = 58
X = 55
The classrooms in the Psychology department are numbered from 100 to 108. A professor records the number of classes held in each room during the fall semester. If these values are presented in a frequency distribution graph, what kind of graph would be appropriate? a bar graph a histogram a histogram or a polygon a polygon
a histogram or a polygon
The null hypothesis states that the sample mean (after treatment) is equal to the original population mean (before treatment). True False
false
For a negatively skewed distribution with a mean of M = 20, what is the most probable value for the median? less than 20 greater than 20 20 0
greater than 20
After measuring two individuals, a researcher can say that Tom's score is four points higher than Bill's. The measurements must come from a(n) ____ scale. ordinal nominal interval or ratio interval
interval or ratio
A distribution of scores has a mean of µ = 50. One new score is added to the distribution and the new mean is found to be µ = 48. From this result, you can conclude that the new score was ____. between 50 and 52 less than 50 greater than 50 equal to 48
less than 50
The students in a psychology class seemed to think that the midterm exam was very easy. If they are correct, what is the most likely shape for the distribution of exam scores? positively skewed negatively skewed normal symmetrical
negatively skewed
What is the shape of the distribution for the following set of data? Scores: 1, 2, 3, 3, 4, 4, 4 5, 5, 5, 5, 6 symmetrical negatively skewed cumulative positively skewed
negatively skewed
A researcher records the change in weight (gain or lost) during the first semester of college for each individual in a group of 25 freshmen, and calculates the average change in weight. The average is an example of a ____. parameter variable statistic constant
statistic
For the following frequency discrete distribution of exam scores, what is the lowest possible reported score on the exam? X f 90-94 3 85-89 4 80-84 5 75-79 2 70-74 1 x = 70 x = 74 x = 90 x=94
x=70
A normal distribution has a mean of µ = 40 with σ = 10. What proportion of the scores in this distribution are greater than X = 55? 0.3085 0.9332 0.0668 0.6915
0.0668
A random sample of n = 16 scores is obtained from a normal population with µ = 40 and σ = 8. What is the probability that the sample mean will be within 2 points of the population mean? 0.3830 0.9544 0.8664 0.6826
0.6826
If a treatment has a very small effect, then what is a likely outcome for a hypothesis test evaluating the treatment? Correctly fail to reject the null hypothesis A Type I error Correctly reject the null hypothesis A Type II error
A Type II error
A researcher administers a treatment to a sample of participants selected from a population with µ = 80. If a hypothesis test is used to evaluate the effect of the treatment, which combination of factors is most likely to result in rejecting the null hypothesis? A sample mean near 80 with α = .05 A sample mean much different than 80 with α = .05 A sample mean near 80 with α = .01 A sample mean much different than 80 with α = .01
A sample mean much different than 80 with α = .05
A sample is obtained from a population with μ = 100 and σ = 20. Which of the following samples would produce the most extreme z-score? A sample of n = 25 scores with M = 102 A sample of n = 25 scores with M = 104 A sample of n = 100 scores with M = 102 A sample of n = 100 scores with M = 104
A sample of n = 100 scores with M = 104
If a set of exam scores forms a symmetrical, non-uniform distribution, what can we conclude about the students' scores? Most of the students had relatively high scores. About 50% of the students have scores above the average, and 50% of the students have scores below the average. It is not possible the draw any conclusions about the students' scores. Most of the students had relatively low scores.
About 50% of the students have scores above the average, and 50% of the students have scores below the average.
Which of the following will increase the power of a statistical test? Change the sample size from n = 25 to n = 100 Change α from .05 to .01 None of the other three options will increase the power. Change from a one-tailed test to a two-tailed test
Change the sample size from n = 25 to n = 100
The critical boundaries for a hypothesis test are z = +1.96 and 1.96. If the z-score for the sample data is z = 1.90, then what is the correct statistical decision? Reject H0 Fail to reject H0 Fail to reject H1 Reject H1
Fail to reject H0
A sample with M = 85 and s = 12 is transformed into z-scores. After the transformation, what are the values for the mean and standard deviation for the sample of z-scores? M = 0 and s = 1 M = 85 and s = 1 M = 85 and s = 12 M = 0 and s = 12
M = 0 and s = 1
What is the value of SS (sum of squared deviations) for the following set of scores? If the scores constitute a population, what is the population standard deviation, s? Scores: 1, 1, 4, 0. SS = 9 and s = 2 SS = 9 and s = 1.5 SS = 16 and s = 2 SS = 16 and s = 1.5
SS = 9 and s = 1.5
A random sample of n = 36 scores is selected from a population. Which of the following distributions will definitively be normal? None of the distributions - the sample, the population, the distribution of sample means - will definitely be normal. The scores in the sample will form a normal distribution. The distribution of sample means will form a normal distribution. The scores in the population will form a normal distribution.
The distribution of sample means will form a normal distribution.
A researcher conducts a hypothesis test to evaluate the effect of a treatment. The hypothesis test produces a z-score of z = 2.37. Assuming that the researcher is using a two-tailed test, what decision should be made? The researcher should reject the null hypothesis with α = .05 but not with α = .01. The researcher should ignore the results. The researcher should reject the null hypothesis with either α = .05 or α = .01. The researcher should fail to reject H0 with either α = .05 or α = .01.
The researcher should fail to reject H0 with either α = .05 or α = .01.
When is there a risk of a Type II error? The risk of a Type II error is independent of the decision from a hypothesis test. Whenever H0 is rejected Whenever H1 is rejected Whenever the decision is "fail to reject H0"
Whenever the decision is "fail to reject H0"
For a particular sample of size n=10, the largest distance (deviation) between a score and the mean is 11 points. The smallest distance between a score and the mean is 4 points. Therefore, the standard deviation will be ____. between 4 and 11 greater than 11 equal to 0 less than 4
between 4 and 11
In a correlational study, ____. one variable is measured and there is only one group of participants one variable is measured and two groups are compared two variables are measured and there is only one group of participants two variables are measured and two groups are compared
two variables are measured and there is only one group of participants
The distribution of sample means ____. will be normal if either the population is normal or the sample size is n > 30 will be normal only if the population distribution is normal will be normal only if the sample size is at least n = 30 is always a normal distribution
will be normal if either the population is normal or the sample size is n > 30
What z-score value separates the top 70% of a normal distribution from the bottom 30%? z = -0.84 z = 0.52 z = -0.52 z = 0.84
z = -0.52
A sample of n = 16 scores is obtained from a population with μ = 50 and σ = 16. If the sample mean is M = 54, then what is the z-score for the sample mean? z = 0.25 z = 0.50 z = 1.00 z = 4.00
z = 1.00
A population of scores has µ = 50 and σ = 5. If every score in the population is multiplied by 3, then what are the new values for the mean and standard deviation? µ = 50 and σ = 5 µ = 50 and σ = 15 µ = 150 and σ = 5 µ = 150 and σ = 15
µ = 150 and σ = 15
You are instructed to subtract four points from each score and find the sum of the resulting values. How would this set of instructions be expressed in summation notation? 4 - ΣX Σ (X - 4) ΣX - 4 Σ(4 - X)
Σ (X - 4)
You have a score of X = 65 on a math exam. The mean score for the class on the exam is μ = 70. Which of the following values for the standard deviation would give you the most favorable position within the class? σ = 0 σ = 10 σ = 1 σ = 5
σ = 10
On an exam with μ = 52, you have a score of X = 56. Which of the following values for the standard deviation would give you the highest position in the class distribution? σ = 10 σ = 2 σ = 8 σ = 4
σ = 2
A population has μ = 50. What value of σ would make X = 55 a more central, representative score in the population? σ = 1 σ = 5 σ = 10 σ = 20
σ = 20
