AP Statistics Identify Inference Procedure

The body's natural electrical field helps wounds heal. If diabetes changes this field, it might explain why people with diabetes heal more slowly. A study of this idea compared randomly selected normal mice and randomly selected mice bred to spontaneously develop diabetes. the investigators attached sensors to the right hip and the front feet of the mice and measured the difference in electrical potential (in millivolts) between these locations. Graphs of the data for each group reveal no outliers or strong skewness. The following computer output provides numerical summaries of the data. Identify the correct inference procedure to use.

• One-sample t test

• Two-sample t test

• Paired t-test

• Regression t-test

• Two-sample z test

Can physical activity in youth lead to mental sharpness in old age? A 2010 study investigating this question involved 9344 randomly selected, mostly white women over age 65 from four U.S. states. These women were asked about their levels of physical activity during their teenage years, 30's, 50's, and later years. Those who reported being physically active as teens enjoyed the lowest level of cognitive decline, only 8.5% had cognitive impairment, compared with 16.7% of women who reported not being physically active at that time. What is the appropriate inference procedure to do for this situation?

• Paired t test

• Two-sample t test

• One-proportion z test

• Two-proportion z test

• Chi-square test of independence

The germination rate of seeds is defined at the proportion of seeds that sprout and grow when properly planted and watered. A certain variety of grass seed usually has a germination rate of 0.80. A company wants to see if spraying the seeds with a chemical that is known to increase germination rates in other species will increase the germination rates of this variety of grass. The company researchers spray a random sample of 400 grass seeds with the chemical, and 339 of the seeds germinate. What is the appropriate inference procedure to use for this situation.

• One-sample t test

• One-proportion z test

• Paired t test

• Chi square test of indepenence

• Chi square goodness of fit

Researchers studied the behavior of bird that were searching for seeds and insects in an Oregon forest. In this forest, 54% of the trees are Douglas firs, 40% are ponderosa pines, and 6% are other types of tress. At a randomly selected time during the day, the researchers observed 156 red-breasted nut-hatches: 70 were see in Douglas firs, 79 in ponderosa pines, and 7 in other types of trees. What is the approrpiate inference procedure for this situation?

• One-proportion z test

• Two-proportion z test

• Chi square test of independence

• Chi square goodness of fit

• Two-sample t test

A company produces candles. Machine 1 make candles with a mean length of 14 cm and a standard deviation of 0.15 cm. Machine 2 makes candles with a mean length of 15 cm and a standard deviation of 0.10 cm. A random sample of 49 candles is taken from each machine. Do the data provide convincing evidence of a difference in the mean lengths of the candles? What is the appropriate inference procedure for this situation?

• 1-proportion z test

• 2-proportion z test

• One-sample t test

• Two-sample t test

• Paired t test

The power takeoff driveline on tractors used in agriculture can be a serious hazard to operators of farm equipment. The driveline is covered by a shield in new tractors, but the shield is often missing on older tractors. Two types of shields are the bolt-on and the flip-up. It was believed that the bolt-on shield was perceived as a nuisance by the operators and deliberately removed, but the flip-up shield is easily lifted for inspection and maintenance and may be left in place. In a study by the U.S. National Safety Council, random samples of older tractors with both types of shields were taken to see what proportion of shields were removed. Of the 183 tractors designed to have bolt-on shields, 35 have been removed. Of the 136 tractors with flip-up shields, 15 were removed. What is the appropriate inference procedure for this situation?

• One-proportion z test

• Two-proportion z test

• Two-Sample t test

• Paired t-test

• Chi square test of independence

Researchers wondered whether maintaining a patient's body temperature close to normal by heating the patient during surgery would affect rates of infection of wounds. Patients were assigned at random to two groups: the normothermic group (core temperatures were maintained at near normal, 36.5 degrees Celsius) and the hypothermic group (core temperatures were allowed to decrease to about 34.5 degrees Celsius). If keeping patients warm during surgery alters the chance of infection, patients in the two groups should show a difference in the average length of their hospital stays. What is the correct inference procedure for this situation?

• One-proporiton z test

• Two-proportion z test

• Two-sample t test

• One-sample t test

• Paired t test

"I can't get through my day without coffee" is a common statement from many college students. they assume that the benefits of coffee include staying awake during lectures and remaining more alert during exams and tests. Students in a statistics class designed an experiment to measure memory retention with and without drinking a cup of coffee 1 hour before a test. This experiment took place on two different days in the same week (Monday and Wednesday). Ten students were used. Each student received no coffee or one cup of coffee 1 hour before the test on a particular day. The test consisted of a serious of words flashed on a screen, after which the students had to write down as many of the words as possible. On the other day, each student received a different amount of coffee (none or one cup). What is the correct inference procedure for this situation?

• One-proporiton z test

• Two-proportion z test

• One-sample t test

• Two-sample t test

• Paired t test

A drug manufacturer forms tablets by compressing a granular material that contains the active ingredient and various fillers. The hardness of a sample from each batch of tablets produced is measured to control the compression process. The target value for the hardness is 11.5. Is there convincing evidence that the mean hardness of the tablets in this batch differs from the target value? Select the appropriate inference procedure for this test.

• One-proportion z test

• Two-proportion z test

• One-sample t test

• Two-sample t test

• Paired t test

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 fully charged batteries by playing a video repeatedly until the battery dies. The quality-control department will discard the batteries from that day's production run if they find convincing evidence that ht mean batter life is less than 10.5 hours. What is the appropriate inference procedure for this data?

• One-proportion z test

• Two-proportion z test

• One-sample t test

• Two-sample t test

• Paired t test