An expert reviews a sample of 10 scientific articles (n=10) and records the following number of errors in each article: 0, 4, 2, 8, 2, 3, 1, 0, 5, and 7. Compute the SS, the variance, and the standard deviation for this sample using the definitional and computational formulas.

A behavioral researcher measures the stress response of mice exposed to scary animal pictures (cat, dog, lion, Cheshire cat) with a GABA sensor implanted in the brain. He uses randomly assigned 40 mice, 10 in each group. The researcher records the amount of stress after 30 seconds assuming that there is no difference in the response in whatever way the mouse is scared. The data is normally distributed. Means and variances are provided in the table below. Is there a difference in the response to scary animals. Group 1 - Cat n₁=10 m₁ = 10 s² 1= 1.8 Group 2 - Dog n2=10 m₂= 5.0 s²2= 3.4 Why is the scare effect so low in group 4? Group 3 - Lion n3=10 m3= 3.4 s²1= 2.5 Group 4 - Chesire Cat n4=10 m4= 2.4 s² 1= 1.6

Explain the circumstances under which we would need to pool the variance for an independent samples t-test

Give a 99.8% confidence interval, for μ₁ −μ₂ given the following information. n₁ = 35, x₁ = 1 2.41, s₁ = 0.39 81 n₂ = 20, x₂ = 2.62, s₂ = 0.83 2 -0.21 ✓0.69 X Use Technology Rounded to 2 decimal places.

A researcher decides to measure anxiety in group of bullies and a group of bystanders using a 23-item, 3 point anxiety scale.  Assume scores on the anxiety scales are normally distributed and the variance among the group of bullies and bystanders are the same. A group of 30 bullies scores an average of 21.5 with a sample standard deviation of 10 on the anxiety scale.  A group of 27 bystanders scored an average of 25.8 with a sample standard deviation of 8 on the anxiety scale. You do not have any presupposed assumptions whether bullies or bystanders will be more anxious so you formulate the null and alternative hypothesis based on that.

A researcher wants to measure average cardiovascular health of university students and compare those scores to the average scores in the general population. Assuming that population variance is known, what statistical test is most appropriate for this study?        independent-samples t-test     single-sample t-test     z-test for sample mean     related-samples t-test

In an industrial experiment, a job was performed by 10 workers using Method I, and by 7 workers using Method II. The experiment yielded the following data. The unit of measurement is minute. A statistician wants to test for the equality of two variances and the difference in the mean times to complete the job using the two methods. (This is a case of two independent samples drawn from two normal populations).  Method 1 Method 2 12221915101615222613 61071261012 n1=10 Mean=17 Variance=26 n2=7 Mean=9 Variance=7 (a) Test at the 5% significance level whether the two variances are equal. (Give null and the alternative hypotheses, test statistic, rejection rule, conclusion)  (b) Estimate with 95% confidence the ratio of the two population variances. Briefly describe what the interval estimate tells you.  (c) Briefly explain how to use the interval estimate in part (b) to test the hypotheses in (a).

An HIV clinical trial with 1151 subjects was conducted. We will focus on two variables from this trial: IVDrug and Age. IVDrug is a categorical variable that indicates whether each subject never, previously, or currently uses IV drugs. Age lists the subject's age in year. Thus, we have age for subjects in three treatment groups. Assume that the samples were collected independently and come from a normally distributed population with equal variances. An ANOVA is used to test whether average age in the three IV drug groups is the same. A partially filled-in ANOVA table is listed below. Use a significance level of 0.05. p-value Treatment Error Total df SS MS 76.77 F 7.5586