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essentials of statistics

Questions and Answers of Essentials Of Statistics

10.25 An independent-samples t test, gender, and talkativeness: “Are Women Really More Talkative Than Men?” is the title of an article that appeared in the journal Science. In the article, Mehl
10.24 An independent-samples t test and getting ready for a date: In an example, we sometimes use in our statistics classes, several semesters’ worth of male and female students were asked how
10.23 The independent-samples t test, hypnosis, and the Stroop effect: Using data from Exercise 9.61 on the effects of posthypnotic suggestion on the Stroop effect (Raz et al., 2005), let’s conduct
10.22 Making a decision: Numeric results for several independent-samples t tests are presented here. Decide whether each test is statistically significant, and report each result in the standard APA
10.21 Find the critical t values for the following data sets:a. Group 1 has 21 participants and Group 2 has 16 participants. You are performing a two-tailed test with an alpha of 0.05.b. You studied
10.20 Consider the following data from two independent groups: Liberals: 2, 1, 3, 2 Conservatives: 4, 3, 3, 5, 2, 4a. Calculate s 2 for each group.b. Calculate dfX, dfY , and dftotal.c. Determine the
10.19 Consider the following data from two independent groups: Group 1: 97, 83, 105, 102, 92 Group 2: 111, 103, 96, 106a. Calculate s 2 for Group 1 and for Group 2.b. Calculate dfX, dfY , and
10.18 In the next column are several sample means. For each class, calculate the differences between the means for students who sit in the front versus the back of a classroom. Mean test grades
10.17 How do we interpret effect size using Cohen’s d?
10.16 For an independent-samples t test, what is the difference between the formula for the t statistic and the formula for Cohen’s d?
10.15 Explain how we determine standard deviation (needed to calculate Cohen’sd) from the several steps of calculations we made to determine standard error.
10.14 Why does the effect-size calculation use standard deviation rather than standard error?
10.13 How does the size of the confidence interval relate to the precision of the prediction?
10.12 What is the difference between pooled variance and pooled standard deviation?
10.11 How do confidence intervals relate to margin of error?
10.10 Define the symbols in the following formula: s 2 difference = s 2 MX + s 2 MY
10.9 Why would we want the variability estimate based on a larger sample to count more (to be more heavily weighted) than one based on a smaller sample?
10.8 What is pooled variance?
10.7 What is the difference between 8 and s?
10.6 As measures of variability, what is the difference between standard deviation and variance?
10.5 As they relate to comparison distributions, what is the difference between mean differences and differences between means?
10.4 Explain how the paired-samples t test helps us evaluate individual differences and the independent-samples t test helps us evaluate group differences.
10.3 What are independent events?
10.2 Explain random assignment and what it controls.
10.1 When is it appropriate to use an independent-samples t test?
9.61 Hypnosis and the Stroop effect: In Chapter 1, you were given an opportunity to complete the Stroop test, in which color words are printed in the wrong color; for example, the word red might be
9.60 Political bias in academia and a paired-samples t test: The following is an excerpt from the abstract (brief opening summary) from a published research study that examined a reported bias
9.59 Death row and the single-sample t test: The Florida Department of Corrections publishes an online death row fact sheet. It reports the average time on death row prior to execution as 11.72 years
9.58 Paid days off and the single-sample t test: The number of paid days off (e.g., vacation, sick leave) taken by eight employees at a small local business is compared to the national average. You
9.56 A paired-samples t test and English-language tests for international students: The International English Language Testing System (IELTS) is a test that assesses the English-language skills of
9.55 Paired-samples t test, decorations in kindergarten classrooms, and science learning: Psychology researcher Anna Fisher and her colleagues studied whether kindergarten students learned better in
9.54 Paired-samples t tests, confidence intervals, and weddingday weight loss: It seems that 14% of engaged women buy a wedding dress at least one size smaller than their current size. Why? Cornell
9.53 Attitudes toward statistics and the paired-samples t test: A professor wanted to know if her students’ attitudes toward statistics changed by the end of the course, so she asked them to fill
9.52 Paired-samples t test and graduate admissions: Is it harder to get into graduate programs in psychology or in history? We randomly selected five institutions from among all U.S. institutions
9.51 Paired-samples t tests, confidence intervals, and hockey goals: Below are the numbers of goals scored by the leading scorers on the New Jersey Devils ice hockey team in the 2007–2008 and
9.50 Brain exercises and a paired-samples t test: PowerBrainRx, a Hong Kong–based for-profit company, promises to improve cognition. Its Web site lists testimonials, including one from a parent
9.49 A single-sample t test and Victoria’s Secret perfume as an insect repellent: Biology researchers examined the mosquitorepelling effects of a control (no scent), insect repellents that contain
9.48 Cultural change and replication: Psychologist Patricia Greenfield (2017) points out that failures to replicate do not necessarily indicate that the initial findings were wrong. She explains:
9.47 Cheating and a single-sample t test: Participants in a study (Chou, 2015) aimed at understanding cheating behaviors were asked to flip a coin 20 times and report—on the honor system—how many
9.46 t tests and the cost of Levi’s jeans and H&M dresses in Halifax: Numbeo is a crowdsourced Web site that gathers data on cities and countries around the world (numbeo.com/cost-of-living). The
9.45 Single-sample t test, military training, and anger: Bardwell, Ensign, and Mills (2005) assessed the moods of 60 male U.S.Marines following a month-long training exercise conducted in cold
9.44 t statistics and standardized tests: On its Web site, the Princeton Review claims that students who have taken its course improve their Graduate Record Examination (GRE) scores, on average, by
9.43 The relation between the z distribution and the t distributions: For the hypothesis tests described in parts (a) through (c), identify what the critical z value would have been if there had been
9.42 Assume we know the following for a paired-samples t test: N = 32, Mdifference = 1.75, s = 4.0.a. Calculate the t statistic.b. Calculate a 95% confidence interval for a two-tailed test.c.
9.40 Consider the following data.Score 1 Score 2 23 16 30 12 28 25 30 27 14 6a. Calculate the paired-samples t statistic.b. Calculate the 95% confidence interval.c. Calculate the effect size. 9.41
9.38 The following are mood scores for 12 participants before and after watching a funny video clip (lower values indicate better mood).Before After Before After 7 2 4 2 5 4 7 3 5 3 4 1 7 5 4 1 6 5 5
9.37 The following are scores for eight students on two different exams. Exam 1 Exam 2 92 84 67 75 95 97 82 87 73 68 59 63 90 88 72 78a. Calculate the paired-samples t statistic for these exam
9.36 Assume eight participants completed a mood scale before and after watching a funny video clip.a. Identify the critical t value for a one-tailed, paired-samples t test with an alpha level of
9.35 Identify critical t values for each of the following tests:a. A one-tailed, paired-samples t test performed on beforeand-after scores on the Marital Satisfaction Inventory for 18 people who
9.34 Market researchers collected information on smartphone data usage for Uber drivers. They wondered if Uber drivers use a higher amount of smartphone data compared to all other taxi drivers. A
9.33 Identify the critical t values for each of the following tests:a. Researchers wanted to know if marriage counseling improved participants’ marital satisfaction. Scores were collected on the
9.32 Using Cohen’s conventions, interpret the effect sizes that you calculated in:a. Exercise 9.30cb. Exercise 9.31c
9.31 Assume we know the following for a two-tailed, single-sample t test: μ = 7, N = 41, M = 8.5, s = 2.1.a. Calculate the t statistic.b. Calculate a 99% confidence interval.c. Calculate the effect
9.30 Assume we know the following for a two-tailed, single-sample t test, at an alpha level of 0.05: μ = 44.3, N = 114, M = 43, s = 5.9.a. Calculate the t statistic.b. Calculate a 95% confidence
9.29 Identify the critical t values for each of the following tests:a. A single-sample t test examining scores for 26 participants to see if there is any difference compared to the population, using
0.01
9.28 Calculate degrees of freedom and identify the critical t value for a single-sample t test in each of the following circumstances:a. Two-tailed test, N = 8, alpha level of 0.10b. One-tailed test,
9.27 Identify the critical t value in each of the following circumstances:a. One-tailed test, df = 73, alpha level of 0.10b. Two-tailed test, df = 108, alpha level of 0.05c. One-tailed test, df = 38,
9.26 For the data 1.01, 0.99, 1.12, 1.27, 0.82, 1.04, calculate the standard deviation under the conditions in parts (a) and (b). Then, complete parts (c) and (d). (Note: You will have to carry some
9.25 For the data 93, 97, 91, 88, 103, 94, 97, calculate the standard deviation under the conditions in parts (a) and (b). Then, complete parts (c) and (d).a. For this sampleb. As an estimate of the
9.24 We use formulas to describe calculations. Find the error in each of the following formulas. Explain why each is incorrect and provide a correction.
9.23 If an effort to replicate a study fails, what are two things that the failure could indicate about the original study?
9.22 What is the appropriate effect size for a paired-samples t test? How is the calculation different from the effect size for a singlesample t test?
9.21 Why is a confidence interval more useful than a single-sample t test or a paired-samples t test?
9.20 If we calculate the confidence interval around the sample mean difference used for a paired-samples t test, and it does not include the value of 0, what can we conclude?
9.19 If we calculate the confidence interval around the sample mean difference used for a paired-samples t test, and it includes the value of 0, what can we conclude?
9.18 Why is the population mean almost always equal to 0 for the null hypothesis in the two-tailed, paired-samples t test?
9.17 How is a paired-samples t test different from a single-sample t test?
9.16 How is a paired-samples t test similar to a single-sample t test?
9.14 When do we use a paired-samples t test? 9.15 Explain the distinction between the terms independent samples and paired samples as they relate to t tests.
9.13 What do we mean when we say we have a distribution of mean differences?
9.11 Why is a confidence interval more useful than a single-sample t test? 9.12 What is the appropriate effect size for a single-sample t test?
9.10 Explain what each part of the following statistical phrase means, as it would be reported in APA format: t(4) = 2.87, p = 0.032.
9.9 Why do the t distributions merge with the z distribution as sample size increases?
9.8 How are the critical t values affected by sample size and degrees of freedom?
9.7 What does the phrase “free to vary, ” referring to a number of scores in a given sample, mean for statisticians?
9.6 When is it appropriate to use a single-sample t test?
9.5 Define the symbols in the formula for the t statistic:
9.4 Explain why the standard error for the distribution of sample means is smaller than the standard deviation of sample scores.
9.3 How is the calculation of standard error different for a t test than for a z test?
9.2 Why do we modify the formula for calculating standard deviation when using t tests (and divide by N − 1)?
9.1 When should we use a t distribution?
8.65 Effect size and an intervention to increase college applications: Caroline Hoxby and Sarah Turner (2013) conducted an experiment to determine whether a simple intervention could increase the
8.64 Sample size, effect size, and ESP: Bem (2011) reports nine experiments in which he presents evidence for extrasensory perception (ESP). For example, in Experiment 1, participants were shown two
8.63 Fantasy baseball: Your roommate is reading Fantasyland: A Season on Baseball’s Lunatic Fringe (Walker, 2006) and is intrigued by the statistical methods used by competitors in fantasy baseball
8.62 Meta-analysis and an examination of whether sex and violence sell: Researchers from The Ohio State University conducted a meta-analysis of 53 studies totaling almost 8500 participants (Lull &
8.61 Meta-analysis and math performance: Following is an excerpt of an abstract from a published meta-analysis by Lindberg and colleagues (2010). Use this excerpt to describe what is done in each of
8.60 Meta-analysis, mental health treatments, and cultural contexts (continued): The research paper on culturally targeted therapy described in the previous exercise reported the following:Across all
8.59 Meta-analysis, mental health treatments, and cultural contexts: A meta-analysis examined studies that compared two types of mental health treatments for ethnic and racial minorities—the
8.58 Effect size and homeless families: A New York Times article reported on the growing problem of homelessness among families (Bellafante, 2013). The reporter wrote that families in a city-run
8.56 Power analysis and enhancing memory: In a study of the effects of testing on enhancing memory, Akan and colleagues (2018) performed an a priori power analysis to determine the sample size they
8.55 Confidence intervals, effect sizes, and tennis serves (continued): As in the previous exercise, assume the average speed of a serve in women’s tennis is around 118 mph, with a standard
8.54 More about confidence intervals, effect sizes, and tennis serves: Let’s assume the average speed of a serve in women’s tennis is around 118 mph, with a standard deviation of 12 mph. We
8.53 Confidence intervals, effect sizes, and Valentine’s Day spending: According to the Nielsen Company, Americans spend $345 million on chocolate during the week of Valentine’s Day. Let’s
8.52 Effect size and English-language tests for international students (continued): In the previous exercise, you calculated an effect size for data for 63 international students at the University of
8.51 Effect size and English-language tests for international students: In the two previous exercises, we considered the IELTS listening module, for which the population of all IELTS takers in a year
8.50 Confidence intervals and English-language tests for international students (continued): Using the IELTS listening data presented in the previous exercise, practice evaluating data using
8.49 Confidence intervals and English-language tests for international students: The International English Language Testing System (IELTS) has six modules, one of which assesses listening skills.
8.48 Confidence intervals, effect sizes, and tennis serves: Let’s assume the average speed of a serve in men’s tennis is around 135 mph, with a standard deviation of 6.5 mph. Because these
8.47 Overlapping distributions and English-language tests for international students: International students who wish to study at English-speaking universities in Canada or the United States are

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