Statistical Procedures - GRE Subject Test: Psychology
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Which of the following statistical tools has one mode and 99.7% of the data falls within three standard deviations of the mean?
Which of the following statistical tools has one mode and 99.7% of the data falls within three standard deviations of the mean?
A bell curve, or normal distribution, is a symmetrical curve with the mode (which also correlates to the mean and median) at the highest point of the curve. The mode is the value most frequently occuring in a set of variables. The mean is the average of a set of values. How spread out the curve is determined by the data set's standard deviation.
A learning curve plots one variable on the x-axis and another on the y-axis. An example of a learning curve could be experience plotted against learning. A person who learns quickly will have a learning curve convex to the vertical axis. A Venn diagram consists of two overlapping circles. In the overlap area, items that are similar to the data sets are included. Scatter plots show the observed relationships between different variables. A chi-squared test compares observed data with data the experimenter would expect to obtain.
A bell curve, or normal distribution, is a symmetrical curve with the mode (which also correlates to the mean and median) at the highest point of the curve. The mode is the value most frequently occuring in a set of variables. The mean is the average of a set of values. How spread out the curve is determined by the data set's standard deviation.
A learning curve plots one variable on the x-axis and another on the y-axis. An example of a learning curve could be experience plotted against learning. A person who learns quickly will have a learning curve convex to the vertical axis. A Venn diagram consists of two overlapping circles. In the overlap area, items that are similar to the data sets are included. Scatter plots show the observed relationships between different variables. A chi-squared test compares observed data with data the experimenter would expect to obtain.
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Which of the following post hoc tests applies simultaneously to all pairwise comparisons 
, and is considered conservative if sample sizes are unequal?
Which of the following post hoc tests applies simultaneously to all pairwise comparisons
Named after John Tukey, the Tukey test is based on a studentized range distribution included with many standard psychological and statistical textbooks today. It is flexible enough to be used with all types of pairwise comparisons, including ANOVA and multiple comparison tests; however, it suffers when sample sizes are unequal.
Named after John Tukey, the Tukey test is based on a studentized range distribution included with many standard psychological and statistical textbooks today. It is flexible enough to be used with all types of pairwise comparisons, including ANOVA and multiple comparison tests; however, it suffers when sample sizes are unequal.
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A statistician who determines that the independent variable has no effect when it really does have an effect has committed which of the following errors?
A statistician who determines that the independent variable has no effect when it really does have an effect has committed which of the following errors?
A type II error means that the experimenter has failed to recognize an effect that is present. On the other hand, a type I error indicates that the experimenter has mistakenly stated that the independent variable has an effect when it has no real effect.
A type II error means that the experimenter has failed to recognize an effect that is present. On the other hand, a type I error indicates that the experimenter has mistakenly stated that the independent variable has an effect when it has no real effect.
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Which of the following kinds of diagrams is best to display nominal data?
Which of the following kinds of diagrams is best to display nominal data?
Nominal data is best represented by a bar chart. Nominal data can be variables such as religion. This is because there is no inherent rank. No one religion is statistically “better” than the other; therefore, it would be impossible to place one higher up than another in a rank order scheme.
Nominal data is best represented by a bar chart. Nominal data can be variables such as religion. This is because there is no inherent rank. No one religion is statistically “better” than the other; therefore, it would be impossible to place one higher up than another in a rank order scheme.
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Which of the following can be described as the variable that is changed in an experiment in order to determine its effects on other variables?
Which of the following can be described as the variable that is changed in an experiment in order to determine its effects on other variables?
The correct choice is “independent variable.” The independent variable is changed in order to observe the changes, if any, that it has on the dependent variable or variables. The dependent variable is defined as the variable that changes in response to the independent variable.
The correct choice is “independent variable.” The independent variable is changed in order to observe the changes, if any, that it has on the dependent variable or variables. The dependent variable is defined as the variable that changes in response to the independent variable.
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Which of the following is best defined as the distance that any point is from the mean on a normal distribution?
Which of the following is best defined as the distance that any point is from the mean on a normal distribution?
The distance that any point is from the mean is known as the standard deviation. When looking at a normal distribution, the mean is the middle or arithmetic average of the set and the deviation measures the spread of the data points from this central tendency.
The distance that any point is from the mean is known as the standard deviation. When looking at a normal distribution, the mean is the middle or arithmetic average of the set and the deviation measures the spread of the data points from this central tendency.
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Which of the following is defined as the measurement of variables that have an inherent natural order?
Which of the following is defined as the measurement of variables that have an inherent natural order?
Ordinal data is used when variables that have an inherent natural order, such as the collegiate class structure: freshman, sophomore, junior, senior. One must complete every level in order to transcend to the next. Nominal data deals with variables such as religion that do not have an inherent natural order. Interval data deals with things like temperature. Last, ratio data would deal with things like time.
Ordinal data is used when variables that have an inherent natural order, such as the collegiate class structure: freshman, sophomore, junior, senior. One must complete every level in order to transcend to the next. Nominal data deals with variables such as religion that do not have an inherent natural order. Interval data deals with things like temperature. Last, ratio data would deal with things like time.
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Which of the following could be defined as all of the members of a group under consideration in a study?
Which of the following could be defined as all of the members of a group under consideration in a study?
All of the members of a group under consideration are referred to as a population. A sample is the subset of the group under consideration. “Statistic” or “parameter” would be incorrect choices because a statistic represents a measure of a sample, while a parameter refers to a measure of a population.
All of the members of a group under consideration are referred to as a population. A sample is the subset of the group under consideration. “Statistic” or “parameter” would be incorrect choices because a statistic represents a measure of a sample, while a parameter refers to a measure of a population.
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Which of the following best describes a normal distribution?
Which of the following best describes a normal distribution?
A normal distribution is asymptotic because it approaches a curve closely. It is unimodal because of its singular mode, and it is symmetric because both sides are mirror images of each other. There are other kinds of distributions like skewed distributions that are unimodal, asymptotic, and asymmetrical. These descriptions can vary depending on the shape of the distribution.
A normal distribution is asymptotic because it approaches a curve closely. It is unimodal because of its singular mode, and it is symmetric because both sides are mirror images of each other. There are other kinds of distributions like skewed distributions that are unimodal, asymptotic, and asymmetrical. These descriptions can vary depending on the shape of the distribution.
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A parameter measures components of which of the following?
A parameter measures components of which of the following?
A parameter measures a population—the whole group that is being considered. A statistic represents a measure of a sample—a subset of the group that is being considered. For example, if you were conducting a study on Spanish people in your university, then the population would be all of the Spanish people at your university. A sample could be all of the Spanish people in one of your classes.
A parameter measures a population—the whole group that is being considered. A statistic represents a measure of a sample—a subset of the group that is being considered. For example, if you were conducting a study on Spanish people in your university, then the population would be all of the Spanish people at your university. A sample could be all of the Spanish people in one of your classes.
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Which of the following best describes the mean of a Z-score?
Which of the following best describes the mean of a Z-score?
The mean of a Z-score is zero. This means that the score is the same as the mean. A positive or negative Z-score would show that it is above or below the mean and by how many standard deviations.
The mean of a Z-score is zero. This means that the score is the same as the mean. A positive or negative Z-score would show that it is above or below the mean and by how many standard deviations.
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A correlational study most likely possesses which of the following?
A correlational study most likely possesses which of the following?
A correlational study looks at the relationship between two or more variables. For example, the relationship between test scores in math and history classes. It does not try to find a cause and effect between the variables, and the researcher does not manipulate the variables. The researcher is simply trying to see if they possess a relationship or correlation.
A correlational study looks at the relationship between two or more variables. For example, the relationship between test scores in math and history classes. It does not try to find a cause and effect between the variables, and the researcher does not manipulate the variables. The researcher is simply trying to see if they possess a relationship or correlation.
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A distribution that has a tail that is longer on the right side is considered to be which of the following?
A distribution that has a tail that is longer on the right side is considered to be which of the following?
The distribution is positive because its tail goes to toward the right. If it were negative, the tail would go toward the Y-axis, or the left. If a distribution's tail is longer on either side, then it is not a normal distribution. It is not symmetrical and would be classified as a skewed distribution.
The distribution is positive because its tail goes to toward the right. If it were negative, the tail would go toward the Y-axis, or the left. If a distribution's tail is longer on either side, then it is not a normal distribution. It is not symmetrical and would be classified as a skewed distribution.
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What does the following symbol indicate?
What does the following symbol indicate?
This symbol represents a command to find the sum of two or more numbers. This symbol is the Greek letter 'E' and is used in a variety of equations. It is called Epsilon.
This symbol represents a command to find the sum of two or more numbers. This symbol is the Greek letter 'E' and is used in a variety of equations. It is called Epsilon.
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Which of the following terms is defined as the descriptive statistic that measures the degree of the relationship between two variables?
Which of the following terms is defined as the descriptive statistic that measures the degree of the relationship between two variables?
The correct choice is “correlation coefficient.” Independent and dependent variables do not measure anything but are simply components of the study itself. The mode is the value that occurs the most in a set of numbers.
The correct choice is “correlation coefficient.” Independent and dependent variables do not measure anything but are simply components of the study itself. The mode is the value that occurs the most in a set of numbers.
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In a negatively skewed distribution, which of the following is true?
In a negatively skewed distribution, which of the following is true?
In a negatively skewed distribution, the tail of the distribution falls on the left or negative side of the distribution. The mode is always the highest score, followed by the median, and lastly the mean. The opposite is true for a positively skewed distribution. In a normal distribution, the mean, median, and mode are all equal.
In a negatively skewed distribution, the tail of the distribution falls on the left or negative side of the distribution. The mode is always the highest score, followed by the median, and lastly the mean. The opposite is true for a positively skewed distribution. In a normal distribution, the mean, median, and mode are all equal.
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Karen received a raw score of 
on an exam with a mean score of 
and a standard deviation of 
. What is Karen's Z-score?
Karen received a raw score of
The exam had a mean of 
and a standard deviation of 
. Karen received a raw score of 
, which is 
points above the mean. In order to calculate her Z-score you must use the Z-score formula:
Karen's Z score is +2.
You would also be able to guess the correct answer by drawing a picture of a normal curve. You can then see that Karen's score is above the mean, which tells you that her Z-score must be positive.
The exam had a mean of
Karen's Z score is +2.
You would also be able to guess the correct answer by drawing a picture of a normal curve. You can then see that Karen's score is above the mean, which tells you that her Z-score must be positive.
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Carla, Bob, and Jimmy all took the same exam. Carla received a T-score of 65, Bob received a Z-score of 1.25, and Jimmy received a standard score of of 85. Who received the highest Z-score on the exam?
Carla, Bob, and Jimmy all took the same exam. Carla received a T-score of 65, Bob received a Z-score of 1.25, and Jimmy received a standard score of of 85. Who received the highest Z-score on the exam?
In order to determine the answer to this question you must have knowledge of T-scores, standard scores, and Z-scores. T-scores always have a mean of 50 and a standard deviation of 10. Carla had a T-score of 65, which is 1.5 standard deviations above the mean, and is equivalent to a Z-score of 1.5. Bob received a Z score of 1.25, which is lower than Carla's Z-score. Standard scores always have a mean of 100 and a standard deviation of 15. Jimmy received a standard score of 85, which is one standard deviation below the mean and equal to a Z-score of -1. Carla had the highest Z-score.
In order to determine the answer to this question you must have knowledge of T-scores, standard scores, and Z-scores. T-scores always have a mean of 50 and a standard deviation of 10. Carla had a T-score of 65, which is 1.5 standard deviations above the mean, and is equivalent to a Z-score of 1.5. Bob received a Z score of 1.25, which is lower than Carla's Z-score. Standard scores always have a mean of 100 and a standard deviation of 15. Jimmy received a standard score of 85, which is one standard deviation below the mean and equal to a Z-score of -1. Carla had the highest Z-score.
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Dr. G is conducting a research study looking at whether or not a new drug decreases depression. She falsely concludes that the drug is ineffective at decreasing depression. Dr. G has committed which of the following?
Dr. G is conducting a research study looking at whether or not a new drug decreases depression. She falsely concludes that the drug is ineffective at decreasing depression. Dr. G has committed which of the following?
"Type II error" involves failing to reject a null hypothesis when it is false. This occurs when a researcher says that the findings are not significant, when in fact they are. "Type I error" is the opposite, and involves rejecting the null hypothesis when it is true. "Power" is the likelihood of rejecting the null when it is false, and is desirable in a research study. Last, "clinical significance" is similar to power and is what researchers aim for. It is important to note that "type III error" is not a term used in statistics.
"Type II error" involves failing to reject a null hypothesis when it is false. This occurs when a researcher says that the findings are not significant, when in fact they are. "Type I error" is the opposite, and involves rejecting the null hypothesis when it is true. "Power" is the likelihood of rejecting the null when it is false, and is desirable in a research study. Last, "clinical significance" is similar to power and is what researchers aim for. It is important to note that "type III error" is not a term used in statistics.
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Which of the following indicates the average amount of variability observed in particular types of scores (e.g. test scores)?
Which of the following indicates the average amount of variability observed in particular types of scores (e.g. test scores)?
The “standard deviation” is a measure of variability, or spread of scores. This measure is calculated by subtracting each score from the mean, squaring the result, dividing this result by the total number of scores, and finally taking the square root of the last calculation. The “range” is also a measure of variability but its calculation involves subtracting the highest and lowest scores; therefore, it is not an average. The mean, median, and mode are measures of central tendency. The “mean” is the average of all scores. The “median” is the middle score, or average of the two middle scores. Last, the “mode” is the score that occurs most frequently.
The “standard deviation” is a measure of variability, or spread of scores. This measure is calculated by subtracting each score from the mean, squaring the result, dividing this result by the total number of scores, and finally taking the square root of the last calculation. The “range” is also a measure of variability but its calculation involves subtracting the highest and lowest scores; therefore, it is not an average. The mean, median, and mode are measures of central tendency. The “mean” is the average of all scores. The “median” is the middle score, or average of the two middle scores. Last, the “mode” is the score that occurs most frequently.
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