Concept explainers
Example 11.1 looked at a study comparing students who use Facebook and students who do not use Facebook (“Facebook and Academic Performance,” Computers in Human Behavior [2010]: 1237–1245). In addition to asking the students in the samples about GPA, each student was also asked how many hours he or she spent studying each day. The two samples (141 students who were Facebook users and 68 students who were not Facebook users) were independently selected from students at a large, public university. Although the samples were not selected at random, they were selected to be representative of the two populations.
For the sample of Facebook users, the
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INTRODUCTION TO STATISTICS & DATA ANALYS
- In a study that compared average time taken by a men and women to do a certain job, a random sample of 13 men and 13 women at a large industrial complex was taken and the following results were obtained. Men Women ?̅ = 54 ??????? ?̅ = 42 ??????? ? = 6 ??????? ? = 8 ??????? Can we conclude that at 0.01 level that women do the job on average 10 minutes earlier than men? Assume the populations to be normally distributed with equal variances.arrow_forwardQuestion #4. US Universities found that 72% of people are concerned about the possibility that their personal records could be stolen over the Internet. If a random sample of 300 college students at a Midwestern university were taken and 228 of them were concerned about the possibility that their personal records could be stolen over the Internet, could you conclude at the 0.025 level of significance that a higher proportion of the university's college students are concerned about Internet theft than the public at large? Report the p-value for this test. Z0.025 = 1.96arrow_forwardIn this study, ten combat veterans undergoing treatment for PTSD were randomly sampled from a local VA hospital in a study designed to test the efficacy of an anti-anxiety medication in reducing the symptoms of PTSD. Based on clinical animal trials, the researchers predict that the drug should reduce symptoms. t= 1.63, df=9, p=0.064, d= 0.529. Before: M= 48.100, SD=1.370, SE=0.433 After: M= 47.000, SD= 1.491, SE= 0.471 My hypotheses are; H0: μbefore ≤ μafter. H1: μbefore > μafter A. State your findings in APA format: B. How would you explain these findings to someone who has never taken a statistics class? In other words, use clear direct, non-jargon language to explain the results:arrow_forward
- The authors of the article "Adjuvant Radiotherapy and Chemotherapy in Node-Positive Premenopausal Women with Breast Cancer"† reported on the results of an experiment designed to compare treating cancer patients with chemotherapy only to treatment with a combination of chemotherapy and radiation. Of the 154 individuals who received the chemotherapy-only treatment, 76 survived at least 15 years, whereas 98 of the 164 patients who received the hybrid treatment survived at least that long. With p1 denoting the proportion of all such women who, when treated with just chemotherapy, survive at least 15 years and p2 denoting the analogous proportion for the hybrid treatment, p̂1 = (rounded to three decimal places) and p̂2 = (rounded to three decimal places). A confidence interval for the difference between proportions based on the traditional formula with a confidence level of approximately 99% is 0.494 − 0.598 ± (2.58) (0.494)(0.506) 154 + (0.598)(0.402) 164…arrow_forwardIn a study, 10 healthy men were exposed to diesel exhaust for 1 hour. A measure of brain activity (called median power frequency, or MPF in Hz) was recorded at two different locations in the brain both before and after the diesel exhaust exposure. The resulting data are given in the accompanying table. For purposes of this exercise, assume that the sample of 10 men is representative of healthy adult males. Subject MPF (in Hz) Location 1before Location 1after Location 2before Location 2after 1 6.4 8.0 6.9 9.4 2 8.6 12.7 9.5 11.2 3 7.4 8.4 6.6 10.2 4 8.6 9.0 9.0 9.7 5 9.8 8.4 9.6 9.2 6 8.9 11.0 9.0 11.9 7 9.1 14.4 7.9 9.3 8 7.4 11.1 8.1 9.1 9 6.7 7.3 7.2 8.0 10 8.9 11.2 7.4 9.3 Construct a 90% confidence interval estimate for the difference in mean MPF at brain location 1 (in Hz) before and after exposure to diesel exhaust. (Hint: See Example 13.7.) (Use ?d = ?before − ?after. Use a table or technology. Round your answers to two decimal places.)…arrow_forwardA paper investigated the driving behavior of teenagers by observing their vehicles as they left a high school parking lot and then again at a site approximately 1 2 mile from the school. Assume that it is reasonable to regard the teen drivers in this study as representative of the population of teen drivers. MaleDriver FemaleDriver 1.3 -0.3 1.3 0.6 0.9 1.1 2.1 0.7 0.7 1.1 1.3 1.2 3 0.1 1.3 0.9 0.6 0.5 2.1 0.5 (a) Use a .01 level of significance for any hypothesis tests. Data consistent with summary quantities appearing in the paper are given in the table. The measurements represent the difference between the observed vehicle speed and the posted speed limit (in miles per hour) for a sample of male teenage drivers and a sample of female teenage drivers. (Use ?males − ?females. Round your test statistic to two decimal places. Round your degrees of freedom down to the nearest whole number. Round your p-value to three decimal places.) t = df =…arrow_forward
- A paper investigated the driving behavior of teenagers by observing their vehicles as they left a high school parking lot and then again at a site approximately 1 2 mile from the school. Assume that it is reasonable to regard the teen drivers in this study as representative of the population of teen drivers. MaleDriver FemaleDriver 1.4 -0.2 1.2 0.5 0.9 1.1 2.1 0.7 0.7 1.1 1.3 1.2 3 0.1 1.3 0.9 0.6 0.5 2.1 0.5 (a) Use a .01 level of significance for any hypothesis tests. Data consistent with summary quantities appearing in the paper are given in the table. The measurements represent the difference between the observed vehicle speed and the posted speed limit (in miles per hour) for a sample of male teenage drivers and a sample of female teenage drivers. (Use ?males − ?females. Round your test statistic to two decimal places. Round your degrees of freedom down to the nearest whole number. Round your p-value to three decimal places.) t = df =…arrow_forwardA consumer advocacy group wanted to study whether different airline carriers differed in terms of their delayed flights. In particular, the researchers were interested in the relationship between p1, the proportion of Alpha Airlines flights that were delayed at least 15 minutes, and p2, the proportion of Beta Airlines flights that were delayed at least 15 minutes. A random sample of 1,000 Alpha flights and a separate random sample of 1,000 Beta flights found that 67 of the Alpha fights and 160 of the Beta flights were delayed at least 15 minutes. The conditions for inference were checked and verified. Does this set of samples provide strong evidence that Alpha Airlines has a smaller proportion of flights that are delayed at least 15 minutes than Beta Airlines, at the α = 0.05 significance level? Find the z-table here. A. The test statistic is z = –6.56 and the P-value ≈ 0. Since the P-value ≈ 0 < 0.05, there is not sufficient evidence that Alpha Airlines has fewer delayed…arrow_forwardIn a study of a group of women science majors who remained in their profession and a group who left their profession within a few months of graduation, the researchers collected the data shown here on a self-esteem questionnaire. Leavers Stayers1 = 3.05 2 = 2.92σ1 = 0.71 σ2 = 0.71n1 = 100 n2 = 227At α = 0.05, can it be concluded that there is a difference in the self-esteem scores of the two groups? Use the P-value method.arrow_forward
- Suppose that in a study of 35 million HPV shots examined, the shots were followed in time by 14,000 serious ailments and 32 confirmed deaths. However, suppose in examining a randomly selected control group of 35 million non-vaccinated people of the same age at a particular time A, 0.0413% developed a serious ailment soon after time A, and 0.000089% died soon after time A. What does the comparison of two groups tell us? What are the percentages in the vaccinated group (serious ailments and confirmed deaths), and how to they compare to the nonvaccinated group? Hint: compute the percentages for serious ailments (14,000/35,000,000) and confirmed deaths (32/35,000,000) for the vaccinated group. Compare with the control group. Notice % above. (0,0413% and 0.000089%) Answer here. What can we conclude with high probability, if this comparison between vaccinated and non-vaccinated groups was done many times with the same basic results? Answer here. Can we absolutely rule out that the…arrow_forwardA research article on the effect of multitasking on grade performance describes an experiment in which 62 undergraduate business students were randomly assigned to one of two experimental groups. Students in one group were asked to listen to a lecture but were told that they were permitted to use cell phones to send text messages during the lecture. Students in the second group listened to the same lecture but were not permitted to send text messages. Afterwards, students in both groups took a quiz on material covered in the lecture. Data from this experiment are summarized in the accompanying table.arrow_forwardIn 2010, Seery, Holman, & Silver found that individuals with some history of adversity report better mental health and well-being compared to people with little to no history of adversity. In an attempt to examine this phenomenon, a researcher surveys a group of college students to determine the negative life events they experienced in the last 5 years and their current feeling of well-being. Participants: With 5-10 negative experiences With 2 or fewer negative experiences n=7 n=7 Well-being score of M=48 Well-being score of M=41 SS=325 SS=347 1. State the hypotheses both experimental and statistical 2. Do the results indicate significantly different reports of Well-being? Use a two-tailed test with a=.05. Please show work and state your decision regarding the H0. 3. Compute the estimated Cohen's d to measure the size of the effect. State…arrow_forward
- Holt Mcdougal Larson Pre-algebra: Student Edition...AlgebraISBN:9780547587776Author:HOLT MCDOUGALPublisher:HOLT MCDOUGAL