The average age at which adolescent girls reach their adult height is 16 years. Suppose you have a sample of 29 adolescent girls who are developmentally delayed, and who have an average age at which they reached their adult height of 17.8 years and a sample variance of 77.4 years. You want to test the hypothesis that adolescent girls who are developmentally delayed have a different age at which they reached their adult height than all adolescent girls. Calculate the t statistic: t= (round to one decimal)

A pharmaceutical company makes tranquilizers. It is assumed that the distribution for the length of time they last is approximately normal. Researchers in a hospital used the drug on a random sample of 9 patients. The effective period of the tranquilizer for each patient (in hours) was as follows: 2.5; 2.8; 3.1; 2.3; 2.3; 2.2; 2.8; 2.1; and 2.4.   1.Which distribution should you use for this problem? (Enter your answer in the form z or tdf where df is the degrees of freedom.)    2. Construct a 95% confidence interval for the population mean length of time.  (i) State the confidence interval. (Round your answers to two decimal places.) (     ,     )   (iii) Calculate the error bound. (Round your answer to two decimal places.)

W 1. X A tablet computer manufacturer claims that its batteries last an average of 10.5 hours when playing videos. The quality control department randomly selects 20 tablets from each day's production and tests the batteries by playing a video repeatedly until the battery dies. The quality control department will reject the batteries from that day's production run if the mean battery life is less than 10.5 hours. Here are the data from one day: 10.3 10.0 10.3 10.6 10.5 10.3 10.1 10.6 11.5 10.3 10.3 12.7 10.6 11.3 13.9 12.5 12.4 10.8 10.2 12.2 The quality control department will test the hypotheses where p true mean battery life (in hours) while playing videos for tablets made during that day. Check that the conditions for performing the test are met. Assume the population is normally distributed. 3 e d C Ho:μ = 50 Ha:μl < 50 $ 4 f 25 % V t 6 (6 b Y h ∞ 7 u n * 00 8 ¡ m ( 9 k O Sign out 1 р Mar 29 7

Justin wants to know whether a commonly prescribed drug does improve the attention span of students with attention deficit disorder (ADD). He knows that the mean attention span for students with ADD who are not taking the drug is 2.3 minutes long. His sample of 12 students taking the drug yielded a mean of 4.6 minutes. Justin can find no information regarding σx , so he calculated s2x =1.96. a. Identify the independent and dependent variables.  b. In a sentence, state the null hypothesis being tested.  c. Using symbols, state the null and alternative hypotheses.  d. Determine the critical region using a one-tailed test with alpha = .05. e .Conduct the hypothesis test (Do the math and compare the t-critical and t-obtained values). f. State your conclusions in terms of H0 (Should you reject the H0 or fail to reject/accept the H0). g. Based on your analysis, is there a relationship between the drug and attention span?

Actuaries use various parameters when evaluating the cost of a life insurance policy. The variance of the life spans of a population is one of the parameters used for the evaluation. Each year, the actuaries at a particular insurance company randomly sample 30 people who died during the year (with the samples chosen independently from year to year) to see whether the variance of life spans has changed. The life span data from this year and from last year are summarized below. Current Last Year Year x1 = 75.8 | x,= 76.2 si= 47.61 s3= = 92.16 (The first row gives the sample means and the second row gives the sample variances.) Assume that life spans are approximately normally distributed for each of the populations of people who died this year and people who died last year. Can we conclude, at the 0.05 significance level, that the variance of the life span for the current year, of, differs from the variance of the life span for last year, o,? Perform a two-tailed test. Then complete the…

Bighorn sheep are beautiful wild animals found throughout the western United States. Let x be the age of a bighorn sheep (in years), and let y be the mortality rate (percent that die) for this age group. For example, x = 1, y = 14 means that 14% of the bighorn sheep between 1 and 2 years old died. A random sample of Arizona bighorn sheep gave the following information: x 1 2 3 4 5 y 15.8 17.3 14.4 19.6 20.0   Σx = 15; Σy = 87.1; Σx2 = 55; Σy2 = 1,540.45; Σxy = 272 (a) Find x, y, b, and the equation of the least-squares line. (Round your answers for x and y to two decimal places. Round your least-squares estimates to three decimal places.) x =   y =   b =   ŷ =   +   x

Two samples of n = 5 participants each generate the following data.  Calculate a t-test score for the difference of these two groups. Group 1 Group 2 2 3 3 3 2 2 2 2 1 2     t(8) = 2.86     t(8) = 2.29     t(8) = 2.5     t(8) = 1.11

You are conducting a study to see if the proportion of voters who prefer Candidate A is significantly different from 0.74. Your sample data produce the test statistic z=2.133. Find the p-value accurate to 4 decimal places.

Compute the test statistic