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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 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?
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?
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?
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?
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?
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?
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 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 terms describes a study design in which several groups of different ages are studied over a period of several years?
Sequential cohort studies are a combination of longitudinal and cross-sectional methods insofar as they compare the behaviors or attitudes of specific groups of people over an extended time period.
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Why is it inappropriate to infer casual conclusions from correlative data?
Correlations explain the strength and direction of the relationship between two variables; however, these relationships do not indicate direct causality. For instance, the relationship can be caused by a third variable, called a confounding variable. Correlations—no matter how strong—do not imply causation.
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Which of the following is not a common difficulty associated with the double-blind study protocol?
In a double-blind protocol, both the research participants and the researchers engaging in the study are unaware of which participants are in the control group and which are in the experimental group. This actually makes subsequent meta-analysis of the double-blinded results easier, as a correctly applied double-blindness will remove any of the researcher's biases from the results.
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Melanie is a regular customer at a gun range, where she shoots paper targets with three different types of guns: a rifle, a pistol, and a shotgun. When firing the rifle, Melanie notices that her shots nearly always hit the target, but are evenly spread out throughout the paper's surface. When firing the pistol, Melanie's shots are all grouped within a few inches of each other, with the group overlaying the bull’s-eye on the target. When firing the shotgun, Melanie's shots are also tightly grouped, but the groups of shots are all slightly above the bull’s-eye. Which of the following terms is best describes Melanie's performance with the shotgun compared to her performance with the pistol?
Reliability is the ability of a measure, test, or effect to produce the same result upon repeated trials. In this case reliability was analogous to the grouping of shots on the target irrespective of the placement of the group. Validity is the ability of a test to measure what it is intended to measure or of a treatment to produce the effect it is purported to produce. In this case validity was analogous to the placement of shots on the target—the closer to the bull’s-eye, the more valid the shots.
In the scenario, the shots from the pistol—which hit both the target on the bull’s-eye and were grouped closely together—are valid and reliable. On the other hand, the shotgun shots—which are only grouped together but are not accurate to the bull’s-eye—are equally reliable but less valid.
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A sample of players on a baseball team are chosen to be drug tested. Which of the following methods could league officials use to ensure that the players are randomly selected?
Random selection allows all of the players on the team to have an equal chance of being chosen for testing. Choosing to test only players of a certain age or position, or only testing those that volunteer or have reached a certain statistical benchmark, would exclude a number of the players on the roster from having a chance to be chosen.
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Dana is participating in a study that asks her to press a red button every time the computer screen in front of her shows a letter X.
The computer screen shows a letter "T." Dana presses the red button. Dana's response is considered to be which of the following?
A false alarm is a response that says the target stimulus (in this case, the letter X) has been detected when that stimulus is not present.
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Dr. Crawford believes she has invented a pill to help with student memorization. For a trial experiment, she gathered two groups of twenty students. She gave the twenty students in Group A the “smart pill”, and the twenty students in Group B a sugar pill. After waiting five minutes, both groups of students were given a list of forty words, and were instructed to memorize the entire list in any order. The students were given five minutes to memorize the list. The students were then asked to verbally recite all of the words they could remember in any order within three minutes.
Group A recited an average of fifteen words, while Group B recited an average of ten words.
In this experiment, what is the independent variable?
The independent variable is what the researcher manipulates in order to test his or her hypothesis. In this experiment, Dr. Smart gave one group the smart pill and the other group a sugar pill in order to evaluate the smart pill's effect on student memorization.
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Dr. Crawford believes she has invented a pill to help with student memorization. For a trial experiment, she gathered two groups of twenty students. She gave the twenty students in Group A the “smart pill”, and the twenty students in Group B a sugar pill. After waiting five minutes, both groups of students were given a list of forty words, and were instructed to memorize the entire list in any order. The students were given five minutes to memorize the list. The students were then asked to verbally recite all of the words they could remember in any order within three minutes.
Group A recited an average of fifteen words, while Group B recited an average of ten words.
In this experiment, what is the dependent variable?
The dependent variable is the item actually being measured or analyzed the support or reject the hypothesis. The dependent variable measures the effect of the independent variable.
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Dr. Crawford believes she has invented a pill to help with student memorization. For a trial experiment, she gathered two groups of twenty students. She gave the twenty students in Group A the “smart pill”, and the twenty students in Group B a sugar pill. After waiting five minutes, both groups of students were given a list of forty words, and were instructed to memorize the entire list in any order. The students were given five minutes to memorize the list. The students were then asked to verbally recite all of the words they could remember in any order within three minutes.
Group A recited an average of fifteen words, while Group B recited an average of ten words.
Group A is the __________.
The experimental group is the group assigned to measure the effect of the independent variable. Students in Group A were given the smart pill, and thus their results will be analyzed to measure the effect it had on student memorization.
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Dr. Crawford believes she has invented a pill to help with student memorization. For a trial experiment, she gathered two groups of twenty students. She gave the twenty students in Group A the “smart pill”, and the twenty students in Group B a sugar pill. After waiting five minutes, both groups of students were given a list of forty words, and were instructed to memorize the entire list in any order. The students were given five minutes to memorize the list. The students were then asked to verbally recite all of the words they could remember in any order within three minutes.
Group A recited an average of fifteen words, while Group B recited an average of ten words.
Group B is the _________.
The control group is the group assigned to provide a comparison to the experimental group’s results, in order to measure the effect of the independent variable. Students in Group B were given a sugar pill instead of the smart pill to measure the effect on how many words students could properly recite.
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Dr. Crawford believes she has invented a pill to help with student memorization. For a trial experiment, she gathered two groups of twenty students. She gave the twenty students in Group A the “smart pill”, and the twenty students in Group B a sugar pill. After waiting five minutes, both groups of students were given a list of forty words, and were instructed to memorize the entire list in any order. The students were given five minutes to memorize the list. The students were then asked to verbally recite all of the words they could remember in any order within three minutes.
Group A recited an average of fifteen words, while Group B recited an average of ten words.
What is Dr. Smart’s null hypothesis?
The null hypothesis suggests that the independent variable has no effect in the experiment. If Dr. Crawford’s null hypothesis is supported, then her smart pill has virtually no effect on student memorization. The goal is to reject the null hypothesis with results from the experiment.
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Dr. Crawford believes she has invented a pill to help with student memorization. For a trial experiment, she gathered two groups of twenty students. She gave the twenty students in Group A the “smart pill”, and the twenty students in Group B a sugar pill. After waiting five minutes, both groups of students were given a list of forty words, and were instructed to memorize the entire list in any order. The students were given five minutes to memorize the list. The students were then asked to verbally recite all of the words they could remember in any order within three minutes.
Group A recited an average of fifteen words, while Group B recited an average of ten words.
What sort of experimental design is this?
Independent measures designs describe an experiment in which there are two or more separate groups. In Dr. Crawford’s experiment, the two groups are the students in Group A and Group B. The students do not overlap groups, and are only exposed to one of the two conditions during the experiment.
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