scope of inference assignment

When sampling, which of the following sample sizes will yield the smallest variability in results obtained from repeated sampling from the population?

35

Tessa conducts an experiment and obtains results that are statistically significant. What is meant by "statistically significant"?

It means that the results that Tessa obtained are too unusual to be explained by chance alone.

Over morning announcements, the principal states that only 20% of the senior class turned in their graduation survey. You find the principal's statement hard to believe because the office previously announced that a coupon for a free large pizza would be given to seniors who turn in their graduation survey. At lunch time, you select a random sample of 10 seniors and ask them if they turned in their graduation survey. Six seniors say "yes. Using technology, the student simulated the sample percent of seniors that turned in their survey using 50 random samples of 10 students under the assumption that 20% of all seniors turned in their survey. Here are the results. Is the sample percentage obtained by the student (60%) statistically significant evidence that greater than 20% of seniors turned in their graduation survey?

Yes 0 percent 60 percent or more less than 5 percent

In a large ball pit, 20% of the balls are red. You plan to jump in and randomly select 10 balls. Which statement is true?

You will likely have one to three red balls in your sample.

An inspector selects a random sample of 25 wireless keyboards from today's production line to assess whether or not they work properly. He finds that 24 of the 25 wireless keyboards do work properly. Which of the following conclusions can we draw from this study? A: We can infer that about 96% of the wireless keyboards produced by the manufacturer that day will work properly. B: We can draw conclusions about cause and effect for the population of all wireless keyboards produced today by this manufacturer.

we can conclude A only

Twenty people who claimed to have trouble sleeping volunteered to participate in a sleep study. Half of them were randomly assigned to take10 mg of melatonin 20 minutes before bed and the other half were randomly assigned to listen to soothing music when they went to bed. The volunteers adhered to their treatments for two weeks. At the end of two weeks, the individuals who listened to soothing music reported a greater improvement to their sleep than those who took melatonin. Which of the following conclusions can we draw from this study? A: We can make inferences based on the results of this study to the population of all people who have trouble sleeping. B: We can draw conclusions about cause and effect for people like those who participated in the study.

we can conclude B only

A tennis court official selects a random sample of 50 tennis balls that were slated for use in a highly contested match. He randomly assigns half of them to be subjected to 90 degree heat to replicate the presumed temperature at match time. The other half are run through a machine that replicates the action of hitting the ball 500 times. After the treatments, he inspects the balls for wear and tear. Which of the following conclusions can we draw from this study? A: We can make inferences based on the results of this study for the population of all tennis balls slated for use in the match. B: We can draw conclusions about cause and effect for the population of tennis balls slated for use in the match.

we can conclude Both A and B

A runner would like to know what percentage of people clean up after their dog while walking on public trails. For the next week, he keeps track every time he observes a person cleaning up after their dog (or not) while he runs on the public trail. He found that four out of 20 dog owners do not clean up after their dog. Which of the following conclusions can we draw from this study? A: We can infer that about 25% of all dog owners do not clean up after their dog while walking on the public trail. B: We can draw conclusions about cause and effect for the population of all people who walk their dog on the public trail.

we can conclude neither a nor b

Is the sample mean time until blinking (x̄ = 36 seconds) statistically significant evidence that the true mean time that students can go without blinking is greater than 30 seconds? Use the results to answer the question.

yes 3 percent 36 or more less than 5 percent