A paint manufacturer wished to compare the drying times of two different types of paint. Independent simple random samples of 11 cans of type A and 9 cans of type B were selected and applied to similar surfaces. The drying times, in hours, were recorded. The summary statistics are as follows. Type A Type B X1 76.9 X2 63.7 $1 4.5 s2 5.1 n1 = 11 n2 9 Construct a 98% confidence interval for the difference between the mean drying time for paint of type A and the mean drying time for paint of type B. Round your answer in 2 decimal places

A company that manufactures baseball bats believes that its new bat will allow players to hit the ball 30 feet farther than its current model. The owner hires a professional baseball player known for hitting home runs to hit ten balls with each bat and he measures the distance each ball is hit to test the company's claim. The results of the batting experiment are shown in the following table. Construct a 90 % confidence interval for the true difference between the mean distance hit with the new model and the mean distance hit with the older model. Assume that the variances of the two populations are the same. Let Population 1 be the distances of balls hit with the new model baseball bat and Population 2 be the distances of balls hit with the old model. Round the endpoints of the interval to one decimal place, if necessary. Hitting Distance (in Feet) New Model Old Model 215 234 202 298 224 294 211 246 215 268 248 211 255 226 228 284 247 221 214 259

Choose the appropriate statistical test. When computing, be sure to round each answer as indicated. A dentist wonders if depression affects ratings of tooth pain. In the general population, using a scale of 1-10 with higher values indicating more pain, the average pain rating for patients with toothaches is 6.8. A sample of 30 patients that show high levels of depression have an average pain rating of 7.1 (variance 0.8). What should the dentist determine? 1. Calculate the estimated standard error. (round to 3 decimals). [st.error] 2. What is thet-obtained? (round to 3 decimals). 3. What is the t-cv? (exact value) 4. What is your conclusion? Only type "Reject" or Retain"

6.22 Sleep deprivation, CA vs. OR, Part I. According to a report on sleep deprivation by the Centers for Disease Control and Prevention, the proportion of California residents who reported insufficient rest or sleep during each of the preceding 30 days is 8.0%, while this proportion is 8.8% for Oregon residents. These data are based on simple random samples of 11,545 California and 4,691 Oregon residents. Calculate a 95% confidence interval for the difference between the proportions of Californians and Oregonians who are sleep deprived and interpret it in context of the data.25

Two groups of individuals were compared with respect to a high carbohydrate low- fat diet (LF) and a high-fat low carbohydrate diet (LC). Mood was assessed using a total mood disturbance score where a lower score is associated with a less negative mood. Assuming that the random samples come from independent normal distributions with a common but unknown variance, construct a 95% confidence interval for the difference between the two population means, LC less LF. Group LC LF 28+22.37 28+18.56 28+22.30 28±8.96 n 12 13 mean 47.3 19.3 standard deviation 28.3 25.8

A company that manufactures baseball bats believes that its new bat will allow players to hit the ball 30 feet farther than its current model. The owner hires a professional baseball player known for hitting home runs to hit ten balls with each bat and he measures the distance each ball is hit to test the company's claim. The results of the batting experiment are shown in the following table. Construct a 90 % confidence interval for the true difference between the mean distance hit with the new model and the mean distance hit with the older model. Assume that the variances of the two populations are the same. Let Population 1 be the distances of balls hit with the new model baseball bat and Population 2 be the distances of balls hit with the old model. Round the endpoints of the interval to one decimal place, if necessary. Hitting Distance (in Feet) New Model 246 240 272 262 237 250 247 235 261 216 Old Model 293 232 299 279 239 228 256 292 272 298

A company that manufactures baseball bats believes that its new bat will allow players to hit the ball 3030 feet farther than its current model. The owner hires a professional baseball player known for hitting home runs to hit ten balls with each bat and he measures the distance each ball is hit to test the company’s claim. The results of the batting experiment are shown in the following table. Construct a 90%90% confidence interval for the true difference between the mean distance hit with the new model and the mean distance hit with the older model. Assume that the variances of the two populations are the same. Let Population 1 be the distances of balls hit with the new model baseball bat and Population 2 be the distances of balls hit with the old model. Round the endpoints of the interval to one decimal place, if necessary.  Hitting Distance (in Feet) New Model Old Model 264264 271271 232232 264264 261261 275275 251251 258258 205205 249249 293293 235235 207207…

• Example: A sample of 25 physically and mentally healthy males participated in a sleep experiment in which the percentage of each participant's total sleeping time spent in a certain stage of sleep was recorded. • The variance computed from the sample data was 2.25. Construct 95 percent confidence intervals for o².