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statistical sampling to auditing
Statistical Methods For Psychology 8th Edition David C. Howell - Solutions
In Exercise 5.8, assume that both the mother and child are asleep from 8:00 p.m. to 7:00 a.m.What would the probability be now?
In some homes, a mother’s behavior seems to be independent of her baby’s, and vice versa.If the mother looks at her child a total of 2 hours each day, and the baby looks at the mother a total of 3 hours each day, and if they really do behave independently, what is the probability that they will
Make up a simple example of a situation in which you are interested in conditional probabilities.
Make up a simple example of a situation in which you are interested in joint probabilities.
Which parts of Exercise 5.3 deal with conditional probabilities?
Which parts of Exercise 5.3 deal with joint probabilities?
Assume the same situation as in Exercise 5.2, except that a total of only 10 tickets were sold and that there are two prizes.a. Given that you don’t win first prize, what is the probability that you will win second prize? (The first prize-winning ticket is not put back in the hopper.)b. What is
Assume that you have bought a ticket for the local fire department lottery and that your brother has bought two tickets. You have just read that 1,000 tickets have been sold.a. What is the probability that you will win the grand prize?b. What is the probability that your brother will win?c. What is
Give an example of an analytic, a relative-frequency, and a subjective view of probability.
The rate of depression in women tends to be about twice that of men. A graduate student took a sample of 100 cases of depression from area psychologists and found that 61 of them were women. You can model what the data would look like over repeated samplings when the probability of a case being a
What effect might the suggestion to experimenters that they report effect sizes have on the conclusions we draw from future research studies in Psychology?
Discuss the different ways that the traditional approach to hypothesis testing and the Jones and Tukey approach would address the question(s) inherent in the example of waiting times for a parking space.
Simon and Bruce (1991), in demonstrating resampling statistics, tested the null hypothesis that the mean price of liquor (in 1961) for the 16 “monopoly” states, where the state owned the liquor stores, was different from the mean price in the 26 “private” states, where liquor stores were
In Chapter 1 we discussed a study of allowances for fourth-grade children. We considered that study again in the exercises for Chapter 2, where you generated data that might have been found in such a study.a. Consider how you would go about testing the research hypothesis that boys receive more
Describe the steps you would go through to test the hypothesis that motorists are ruder to fellow drivers who drive low-status cars than to those who drive high-status cars.
Describe the steps you would go through to flesh out the example given in this chapter about the course evaluations. In other words, how might you go about determining whether there truly is a relationship between grades and course evaluations?
In the example in Section 4.11 how would the test have differed if we had chosen to run a two-tailed test?
Rerun the calculations in Exercise 4.18 for a 5 .01.
For the distribution in Figure 4.3, I said that the probability of a Type II error (b) is .74.Show how this probability was obtained.
Give two examples of research hypotheses and state the corresponding null hypotheses.
How would decreasing a affect the probabilities given in Table 4.1?
What is the difference between a “distribution” and a “sampling distribution”?
Define “sampling error.”
In Exercise 4.7 what would be the alternative hypothesis (H1)?
Describe a situation in daily life in which we routinely test hypotheses without realizing it.
In Exercise 4.10 what would we call M in the terminology of this chapter?
Imagine that you have just invented a statistical test called the Mode Test to test whether the mode of a population is some value (e.g., 100). The statistic (M) is calculated as M 5 Sample mode Sample range.Describe how you could obtain the sampling distribution of M. (Note: This is a purely
Why might (or might not) the GRE scores be normally distributed for the restricted sample(admitted students) in Exercise 4.7?
Why is such a small standard deviation reasonable in Exercise 4.7?
A recently admitted class of graduate students at a large state university has a mean Graduate Record Exam verbal score of 650 with a standard deviation of 50. (The scores are reasonably normally distributed.) One student, whose mother just happens to be on the board of trustees, was admitted with
Why might I want to adopt a one-tailed test in Exercise 4.2, and which tail should I choose?What would happen if I chose the wrong tail?
Using the example in Exercise 4.2, describe what we mean by the rejection region and the critical value.
What would be a Type II error in Exercise 4.2?
What would be a Type I error in Exercise 4.2?
For the past year I have spent about $4.00 a day for lunch, give or take a quarter or so.a. Draw a rough sketch of this distribution of daily expenditures.b. If, without looking at the bill, I paid for my lunch with a $5 bill and received $.75 in change, should I worry that I was overcharged?c.
Suppose I told you that last night’s NHL hockey game resulted in a score of 26–13. You would probably decide that I had misread the paper and was discussing something other than a hockey score. In effect, you have just tested and rejected a null hypothesis.a. What was the null hypothesis?b.
The data plotted below represent the distribution of salaries paid to full professors of Psychology with 7–11 years of service in 2008–2009, the last year that data are available.The data are available on the Web site at Ex3-24.dat, which also includes salaries for 241 years in rank. Although
Recently in answer to a question that was sent to me I had to create a set of 16 scores that were more-or-less normally distributed with a mean of 16.3 and a standard deviation of 4.25. The approach taken in Exercise 3.20 could be used to produce data with a mean and standard deviation close to
If you go back to the reaction-time data presented as a frequency distribution in Table 2.2 and Figure 2.1, you will see that for the full set of scores they are not normally distributed.For these data the mean is 60.26 and the standard deviation is 13.01. By simple counting, you can calculate
In Chapter 2, Figure 2.16, I plotted three histograms corresponding to three different dependent variables in Everitt’s example of therapy for anorexia. Those data are available at www.uvm.edu/~dhowell/methods8/DataFiles/Fig2-16.dat. (The variable labels are in the first line of the file.)
Use a standard computer program such as SPSS, OpenStat, or R to generate 5 samples of normally distributed variables with 20 observations per variable. (For SPSS the syntax for the first sample would be COMPUTE norm1 5 RV.NORMAL(0,1). For R it would be norm1
In Section 3.6, I said that T scores are designed to have a mean of 50 and a standard deviation of 10 and that the Achenbach Youth Self-Report measure produces T scores. The data in Figure 3.3 do not have a mean and standard deviation of exactly 50 and 10. Why do you suppose this is so?
Assuming that the Behavior Problem scores discussed in this chapter come from a population with a mean of 50 and a standard deviation of 10, what would be a diagnostically meaningful cutoff if you wanted to identify those children who score in the highest 2% of the population?
What is the 75th percentile for GPA in Appendix Data Set? (This is the point below which 75% of the observations are expected to fall.)
What does the answer to Exercise 3.15 suggest about the importance of reference groups?
For all seniors and non-enrolled college graduates taking the GRE in October 1981, the mean and the standard deviation were 507 and 118, respectively. How does this change the answers to Exercises 3.13 and 3.14?
In Exercise 3.13 what score would be equal to or greater than 75% of the scores on the exam? (This score is the 75th percentile.)
In October 1981, the mean and the standard deviation on the Graduate Record Exam (GRE)for all people taking the exam were 489 and 126, respectively. What percentage of students would you expect to have a score of 600 or less? (This is called the percentile rank of 600.)
Unfortunately, the whole world is not built on the principle of a normal distribution. In the preceding example the real distribution is badly skewed because most children do not have language problems and therefore produce all or most constructions correctly.a. Diagram how the distribution might
A number of years ago a friend of mine produced a diagnostic test of language problems.A score on her scale is obtained simply by counting the number of language constructions(e.g., plural, negative, passive) that the child produces correctly in response to specific prompts from the person
We have sent out everyone in a large introductory course to check whether people use seat belts. Each student has been told to look at 100 cars and count the number of people wearing seat belts. The number found by any given student is considered that student’s score.The mean score for the class
A dean must distribute salary raises to her faculty for the next year. She has decided that the mean raise is to be $2,000, the standard deviation of raises is to be $400, and the distribution is to be normal.a. The most productive 10% of the faculty will have a raise equal to or greater than$ .b.
A certain diagnostic test is indicative of problems only if a child scores in the lowest 10% of those taking the test (the 10th percentile). If the mean score is 150 with a standard deviation of 30, what would be the diagnostically meaningful cutoff?
Under what conditions would the answers to parts (b) and (c) of Exercise 3.6 be equal?
A set of reading scores for fourth-grade children has a mean of 25 and a standard deviation of 5. A set of scores for ninth-grade children has a mean of 30 and a standard deviation of 10. Assume that the distributions are normal.a. Draw a rough sketch of these data, putting both groups in the same
The person in charge of the project in Exercise 3.3 counted only 950 shoppers entering the store. Is this a reasonable answer if he was counting conscientiously? Why or why not?
Using the example from Exercise 3.3:a. What two values of X (the count) would encompass the middle 50% of the results?b. 75% of the counts would be less than ———.c. 95% of the counts would be between ——— and ———.
Suppose we want to study the errors found in the performance of a simple task. We ask a large number of judges to report the number of people seen entering a major department store in one morning. Some judges will miss some people, and some will count others twice, so we don’t expect everyone to
Using the distribution in Exercise 3.1, calculate z scores for X 5 2.5, 6.2, and 9. Interpret these results.
Assume that the following data represent a population with μ 5 4 and s 5 1.63:X 5 [1 2 2 3 3 3 4 4 4 4 5 5 5 6 6 7]a. Plot the distribution as given.b. Convert the distribution in part (a) to a distribution of X – μ.c. Go the next step and convert the distribution in part (b) to a distribution
Do an Internet search using Google to find how to create a kernel density plot using SAS or S-Plus.
Under what conditions will a transformation alter the shape of a distribution?
Draw a boxplot to illustrate the difference between reaction times to positive and negative instances in reaction time for the data in Table 2.1. (These data can be found at this book’s Web site as Tab2-1.dat.)
Compute the 10% Winsorized standard deviation for the data in Table 2.6—Set 32.
Compute the 10% trimmed mean for the data in Table 2.6—Set 32.
Go to Google and find an example of a study in which the coefficient of variation was reported.
For the data in Appendix Data Set, the GPA has a mean of 2.456 and a standard deviation of 0.8614. Compute the coefficient of variation as defined in this chapter.
Compute the coefficient of variation to compare the variability in usage of “and then . . .”statements by children and adults in Exercises 2.1 and 2.4.
Create a boxplot for the variable ADDSC in Appendix Data Set.
Create a boxplot for the data in Exercise 2.4.
Using the results demonstrated in Exercises 2.34 and 2.35, transform the following set of data to a new set that has a standard deviation of 1.00:[5 8 3 8 6 9 9 7].
In Exercise 2.4, what percentage of the scores fall within plus or minus two standard deviations from the mean?
In Exercise 2.1, what percentage of the scores fall within plus or minus two standard deviations from the mean?
Compare the answers to Exercises 2.40 and 2.41. Is the standard deviation for children substantially greater than for adults?
Calculate the range, variance, and standard deviation for the data in Exercise 2.4.
Calculate the range, variance, and standard deviation for the data in Exercise 2.1.
Use SPSS to superimpose a normal distribution on top of the histogram in the previous exercise.(Hint: This is easily done from the pulldown menus in the graphics procedure.)
In one or two sentences, describe what the following graphic has to say about the grade point averages for the students in our sample.
The accompanying output applies to the data on ADDSC and GPA described in Appendix:Data Set. The data can be downloaded as the Add.dat file at this book’s Web site. How do these answers on measures of central tendency compare to what you would predict from the answers to Exercises 2.12 and 2.13?
Create a sample of 10 numbers that has a mean of 8.6. How does this illustrate the point we discussed about degrees of freedom?
Given the following set of data, show that multiplying each score by a constant multiplies all measures of central tendency by that constant:[8 3 5 5 6 2].
Given the following set of data, demonstrate that subtracting a constant (e.g., 5) from every score reduces all measures of central tendency by that constant:[8, 7, 12, 14, 3 7 ].
A group of 15 rats running a straight-alley maze required the following number of trials to perform at a predetermined criterion level:Trials required to reach criterion: 18 19 20 21 22 23 24 Number of rats (frequency): 1 0 4 3 3 3 1 Calculate the mean and median of the required number of trials
Make up a unimodal set of data for which the mean and median are equal but are different from the mode.
Using the positively skewed set of data that you created in Exercise 2.6, does the mean fall above or below the median?
Make up a set of data for which the mean is greater than the median.
The following data from http://www.bsos.umd.edu/socy/vanneman/socy441/trends/marrage.html show society changes of age at marriage over a 50-year period. What trends do you see in the data and what might have caused them?
More recent data on AIDS/HIV world-wide can be found at http://data.unaids.org/pub/EpiReport/2006/2006_EpiUpdate_en.pdf. How does the change in U.S. incidence rates compare to rates in the rest of the world?
The following data represent the number of AIDS cases in the United States among people aged 13–29 for the years 1981 to 1990. This is the time when AIDS was first being widely recognized. Plot these data to show the trend over time. (The data are in thousands of cases and come from two different
The following data represent U.S. college enrollments by census categories as measured from 1976 to 2007. The data are in percentages. Plot the data in a form that represents the changing ethnic distribution of college students in the United States. (The data entries are in thousands.) From
Rogers and Prentice-Dunn (1981) had subjects deliver shock to their fellow subjects as part of a biofeedback study. They recorded the amount of shock that the subjects delivered to white participants and black participants when the subjects had and had not been insulted by the experimenter. Their
The following figure is adapted from a paper by Cohen, Kaplan, Cunnick, Manuck, and Rabin (1992), which examined the immune response of nonhuman primates raised in stable and unstable social groups. In each group, animals were classed as high or low in affiliation, measured by the amount of time
One frequent assumption in statistical analyses is that observations are independent of one another. (Knowing one response tells you nothing about the magnitude of another response.)How would you characterize the reaction-time data in Table 2.1, just based on what you know about how they were
In addition to comparing the three distributions of reaction times, as in Exercise 2.23, how else could you use the data from Table 2.1 to investigate how people process information?
Sternberg ran his original study (the one that is replicated in Table 2.1) to investigate whether people process information simultaneously or sequentially. He reasoned that if they process information simultaneously, they would compare the test stimulus against all digits in the comparison
In Table 2.1 (page 17), the reaction-time data are broken down separately by the number of digits in the comparison stimulus. Create three stem-and-leaf displays, one for each set of data, and place them side-by-side. (Ignore the distinction between positive and negative instances.) What kinds of
Use the data from Exercises 2.14 and 2.15 to show thata. g 1X 1 Y2 5 gX 1 gY.b. gXY 2 gXgY.c. gCX 5 CgX. (where C represents any arbitrary constant)d. aX2 2 AaXB2.
Using the data from Exercises 2.14 and 2.15, record the two data sets side-by-side in columns, name the columns X and Y, and treat the data as paired.a. Calculate gXY.b. Calculate gXgY.c. Calculate gXY 2 gXgY NN 2 1.(You will come across these calculations again in Chapter 9.)
Using the data from Exercise 2.15,a. calculate AgYB2 and gY2.b. calculate gY2 2 AgYB2 NN 2 1c. calculate the square root of the answer for part (b).d. what are the units of measurement for parts (b) and (c)?
Using the data from Exercise 2.14,a. calculate AgXB2 and gX2.b. calculate gX/N, where N 5 the number of scores.c. what do you call what you calculated in part (b)?
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