Imagine a researcher wants to determine whether or not a given drug has any effect on the scores of human subjects performing a task of ESP (Extrasensory perception) sensitivity. He randomly assigns his subjects to one of two groups. Nine hundred subjects in group 1 (the experimental group) receive an oral administration of the drug prior to testing. In contrast, 1000 subjects in group 2 (control group) receive a placebo. For the drug group, the mean score on the ESP test was 9.78, S.D. = 4.05, n = 900 or the placebo group, the mean = 15.10, S.D. = 4.28, n= 1000. Test if there is any effect.
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Imagine a researcher wants to determine whether or not a given drug has any effect on the scores of human subjects performing a task of ESP (Extrasensory perception) sensitivity. He randomly assigns his subjects to one of two groups. Nine hundred subjects in group 1 (the experimental group) receive an oral administration of the drug prior to testing. In contrast, 1000 subjects in group 2 (control group) receive a placebo. For the drug group, the
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- Two separate samples receive two different treatments. The first treatment group (N = 9) has a mean of 50 with SS = 710. The second treatment group (N = 6) has a mean of 60 with SS = 460. Is the second treatment group significantly larger than the first? What is the effect size?One critique of sentencing research is that it generally focuses on the differences between white defendants and defendants of color and rarely examines differences between minority groups. The JDCC data set can be used to test for differences between the sentences received by black and Hispanic juveniles convicted of property crimes. Black juveniles (Sample 1; N = 229) were sentenced to a mean of 31.09 months of probation (s = 15.42), and Hispanic juveniles (Sample 2; N = 118) received a mean of 40.84 months (s = 16.45). Using an alpha level of .01, test the hypothesis that there is a statistically significant difference between the two group means. Assume unequal population variances. Use all five steps.A graduate student is interested in how viewing different types of scenes affects working memory. For his study, he selects a random sample of 36 adults. The subjects complete a series of working memory tests before and after walking in an urban setting. Before the walk, the mean score on the test of working memory was 9.1. After the walk, the mean score was 1.4 higher. The graduate student has no presupposed assumptions about how viewing different types of scenes affects working memory, so he formulates the null and alternative hypotheses as: H00 : μDD = 0 H11 : μDD ≠ 0 Assume that the data satisfy all of the required assumptions for a repeated-measures t test. The graduate student calculates the following statistics for his hypothesis test: Mean difference (MDD) 1.4 Estimated population standard deviation of the differences (s) 1.6 Estimated standard error of the mean differences (sMDMD) 0.2667 Degrees of freedom (df) 35 The t statistic 5.25 The critical values of t…
- Researchers investigate how the presence of cell phones influence the quality of human interaction. Subjects are randomly selected from a population and divided into an experimental group that is asked to leave their phones in the front of the room and a control group that are not asked to leave their cell phones at the front of the room. Subjects are left alone for 10 minutes and then asked to take a survey designed to measure quality of interactions they had with others in the experiment. What statistical test is appropriate?A social psychologist recently developed a childhood-memories test that is intended to measure how people recall pleasant and unpleasant experiences from childhood. Scores on the test range from 1 (very unpleasant) to 100 (very pleasant). The psychologist standardized the test with a large group of college students (ages 18-25), and the mean score was p=60. The test was then given to a sample of n=25 individuals who were all between the ages of 40 and 45. The average score for this sample was 64.3 with SS (sum of squares)=600. Note: S?=SS÷df (variance is equal to sum of squares divided by the degrees of freedom). What is your standard deviation? Answer:There are many ways to measure the reading ability of children. Research designed toimprove reading performance is dependent on good measures of the outcome. Onefrequently used test is the DRP, or Degree of Reading Power. A researcher suspects that themean score µ of all third- graders in Henrico County Schools is different from the nationalmean, which is 32. To test her suspicion, she administers the DRP to an SRS of 44 HenricoCounty third-grade students. The distribution of scores is summarized in the Minitab outputbelow: MEAN STDEV SEMEAN MIN Q1 MEDIAN Q3MAXDRP 35.09 11.19 1.69 14.00 26.00 35.00 44.0054.00 Construct a 90% confidence interval to estimate the mean DRP score in Henrico CountySchools.
- A researcher hypothesizes that different colors of cars result in different average speeds. To test this claim, she took a random sample of 20 people who own 4 different colors of colors of cars (n = 20, N = 80, G = 4), and she then tracks their average speed on the highway for a week of driving. The following ANOVA table has some of her results. Please help her answer her research questions by completing the following ANOVA table below and answering the follow-up questions. Be sure to label your answers with the appropriate letter and show all your work! Source Sums of Squares df Mean Square F Effect (between) Error (within) 100.90 ------ Total 170.10 ------- ------ a) What is the Sums of Squares (SS) between (effect)? b) What are the Mean Square (MS) between (effect) and the MS within (error)? c) What are the degrees of freedom (df) between, the df within, and the df total? d) What is the overall F-statistic? e) Based on the…According to previous studies, the mean distance each visitor in Greenspan National Park hikes during their visit is 21 kilometers. The park recently closed its shuttle system, which used to transport hikers to many of the park's most popular hiking trails. Because of this, an administrator at the park suspects the mean distance, H, is now less than 21 kilometers. The administrator chooses a random sample of 85 visitors. The mean distance hiked for the sample is 20.5 kilometers. Assume the population standard deviation is 8.3 kilometers. Can the administrator conclude that the mean distance hiked by each visitor is now less than 21 kilometers? Perform a hypothesis test, using the 0.10 level of significance. (a) State the null hypothesis H, and the alternative hypothesis H. OSO D-O ? (b) Perform a Z-test and find the p-value. Here is some information to help you with your Z-test. • The value of the test statistic is given by • The p-value is the area under the curve to the left of the…According to previous studies, the mean distance each visitor in Greenspan National Park hikes during their visit is 30 kilometers. The park recently closed its shuttle system, which used to transport hikers to many of the park's most popular hiking trails. Because of this, an administrator at the park suspects the mean distance, u, is now less than 30 kilometers. The administrator chooses a random sample of 45 visitors. The mean distance hiked for the sample is 27.2 kilometers. Assume the population standard deviation is 9.9 kilometers. Can the administrator conclude that the mean distance hiked by each visitor is now less than 30 kilometers? Perform a hypothesis test, using the 0.10 level of significance. (a) State the null hypothesis H, and the alternative hYpothesis H,. OAccording to previous studies, the mean distance each visitor in Greenspan National Park hikes during their visit is 21 kilometers. The park recently closed its shuttle system, which used to transport hikers to many of the park's most popular hiking trails. Because of this, an administrator at the park suspects the mean distance, u, is now less than 21 kilometers. The administrator chooses a random sample of 85 visitors. The mean distance hiked for the sample is 20.5 kilometers. Assume the population standard deviation is 8.3 kilometers. Can the administrator conclude that the mean distance hiked by each visitor is now less than 21 kilometers? Perform a hypothesis test, using the 0.10 level of significance. (a) State the null hypothesis H and the alternative hypothesis H . H: 0 O2. A law school releases admissions data from past years. The median score on the LSAT for accepted students was 167. (Scores on the LSAT range from 120 to 180 points.) The first and third quartiles of LSAT scores for accepted students were 155 and 173 points, respectively. (a) Roughly sketch a histogram for what the LSAT scores for accepted students might look like based on the information given. (b) Suppose you are applying to this law school, and you read about an experiment for a new LSAT test-preparation course. Two hundred students participated. Of these, 100 were randomly chosen to take the course. They got an average score of 166 points, with an SD of 17 points. The other 100 students did not take the course and studied on their own. They got an average score of 165 points, with an SD of 18 points. 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