Question 1

State one advantage and one disadvantage of the median as a measure of central tendency.

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Question 2

If a sample's scores on a test form a normal curve, what is one piece of information that the standard deviation provides?

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Question 3

What does a test of statistical significance of the difference between the mean scores of two groups tell researchers about their null hypothesis?

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Question 4

(a) What is statistical power? (b). Briefly describe two factors that increase statistical power.

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Question 5

A researcher compares the scores of 1,000 randomly selected urban eighth grade students with 1,000 randomly selected rural eighth grade students on a 30-item test of mathematical understanding. The urban sample obtains a mean raw score of 12.6, while the rural sample obtains a mean raw score of 13.2. The standard deviation is 5.1. The difference between the mean scores is significant at the .05 level. Would you consider this difference to be of practical significance? Why or why not?

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Question 6

Explain what confidence limits reveal about the population values based on the findings for a research sample.

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Question 7

What are two advantages of organizing data into a stem-and-leaf display for exploratory data analysis?

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Question 8

Several students in a researcher's sample take a test administered at the start of the study but do not take the test administered at the end of the study. Give one reason why this creates a problem for the research procedure.

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Question 9

A researcher administers a test of musical knowledge to all students in 30 classrooms and then compares the performance of the boys and girls on this test. If the unit of statistical analysis is the classroom, how would the comparison be made?

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Question 10

State one reason why it is desirable to retain one's raw research data for a period of time after a study has been completed.

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Question 11

You want to know the average gain in reading speed that is made by students who take a speed-reading course. A reading test was given to 250 students before and after they took the course. In looking over the scores, you notice that most students gained 100 to 300 words per minute. However, there are about 20 students who made outstanding gains, ranging from 600 to 1,000 words per minute. Would the mean or the median be a more accurate measure of central tendency, and why?

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Question 12

A researcher finds that the mean score of scholarship students on a final exam in a university history course is 89.7, and the mean score of other students is 85.3. A t test of this difference yields a p value of .01. What does the p value tell us about the null hypothesis? Also, what generalization does the p value allow us to make?

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Question 13

A researcher has completed a study in which an experimental group of 60 college students was formed into pairs and was requested to ask each other questions in preparation for an examination. A control group of 60 students was requested to quiz themselves in preparation for the same examination. Students' scores on the examination formed the dependent variable. What is the appropriate unit of statistical analysis for determining whether the examination performance of the experimental group differed from that of the control group?

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Quiz 5: Statistical Techniques