Statistical Based Inference

The dot plots show how long it took students in Mr. Chauncey's two science classes to finish their science homework last night. Find the means to make an inference about the data.

• The 1st period mean is 35. The 2nd period mean is 38.75. On average, it took students in the 1st period class slightly longer to finish their homework than it did the students in the 2nd period class.

• The 1st period mean is 38.75. The 2nd period mean is 35. On average, it took students in the 1st period class slightly longer to finish their homework than it did the students in the 2nd period class.

• The 1st period mean is 35. The 2nd period mean is 38.75. On average, it took students in the 2nd period class slightly longer to finish their homework than it did the students in the 1st period class.

• The 1st period mean is 38.75. The 2nd period mean is 35. On average, it took students in the 2nd period class slightly longer to finish their homework than it did the students in the 1st period class.

A recent survey of 800 seventh graders from across the state shows 4 out of 10 like to play paper football. How many students said they like to play paper football?

• 40 students

• 200 students 

• 320 students

• 8,000 students

There are 400 students at Polly's school. She surveyed a random sample of 80 students to find their favorite hobby. 19 said they like to read. 30 said they like to be with friends. 8 said they like to do crafts. 23 said they like to play sports. Polly infers that doing crafts is the least popular hobby at her school. Refer to the data table. Polly surveys two more samples. Do the results from these samples support the inference made from the first sample?

• Yes, the survey results support the inference that doing crafts is the least popular hobby at Polly's school.

• No, the survey results does not support the inference that doing crafts is the least popular hobby at Polly's school.

There are 400 students at Polly's school. She surveyed a random sample of 80 students to find their favorite hobby. 19 said they like to read. 30 said they like to be with friends. 8 said they like to do crafts. 23 said they like to play sports. Polly infers that doing crafts is the least popular hobby at her school. Yovani estimates that about 200 students in the school favor playing sports as a hobby. Do you agree?

• Yes, I used a proportion to find the number of students in the school who likely to prefer to play sports. 23/80 = 200/400; 200 students

• No, I used a proportion to find the number of students in the school who likely to prefer to play sports. 23/80 = 115/400; 115 students

True or False: all samples lead to a good prediction about an entire population.

• True

• False

A college conducted a survey of randomly selected freshman about their choice of major. The table shows the results of the survey.

What inference about all freshman at this college is best supported by this information?

• The number of freshmen who chose English as their major is less than the number of freshmen who are Undecided on their major.

• The number of freshmen who chose Education as their major is greater than the number of freshmen who chose Science or Other as their major.

• The number of freshmen who chose Business or Education as their major is less than the number of freshmen who chose Science or Engineering as their major.

• The number of freshmen who chose Business as their major is greater than the number of freshmen who chose English as their major.

A researcher asked five of his doctor friends if they thought the new Brand X medicine that he developed was effective. Four responded "yes." The researcher used the results to write a TV advertisement claiming that "4 out of 5 doctors prefer Brand X medicine." Is this a valid inference? Explain.

• No, because the doctors asked are not a representative sample of the population of doctors.

• No, because 4 doctors said yes out of 9 who were asked.

• Yes, because the doctors asked are a representative sample of the population of doctors.

• Yes, because 4 doctors said yes out of the 5 who were asked.

Sampling can be used to make an inference (or educated guess) about a population.

• True

• False

What is one other factor that might be related to BOTH parental education and law school debt?

• Family income

• Type of law school attended

• Undergraduate institution prestige

• Geographical location

• Gender

Litzy collects data from a random sample of 7th graders. Out of 40 respondents, 7 attend afterschool programs. Of the 200 7th graders attending Litzy's school, how many would be expected to attend afterschool programs?

• 14 7th graders

• 28 7th graders

• 35 7th graders

• 42 7th graders