Inference Statistics

Which class has the higher median?

• 1st period

• 2nd period

• They have the same median

What percent of data lies within 1 standard deviation from the mean?

• 95%

• 99%

• 68%

• 100%

Find the Z-score.

Mean = 22

Standard Deviation: 3.1

x = 29

• 2.26

• 16.45

• -2.26

• 1.26

Find the z-score.

Mean = 45

Standard Deviation: 2.1

x = 50

• 2.38

• 3.00

• 3.08

• 2.33

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.

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

• True

• False

The mean weight of Sumo wrestlers is 330 pounds with a standard deviation of 40 pounds. The mean weight of soccer players is 142 pounds with a standard deviation of 5.2 pounds.

A particular Sumo wrestler weighs 360 pounds and a particular Soccer player weighs 153.6 pounds. Who weighs more, relatively speaking? (Who has a higher z score?)

• Sumo wrestler

• Soccer player

• They weigh the same, relatively speaking

If the margin of error in a confidence interval is 4, what is the range of the confidence interval around a sample mean of 50?

• 46 to 54

• 48 to 52

• 45 to 55

• 49 to 51

A confidence interval for the mean score of a test is (75, 85). What is the margin of error?

• 5

• 10

• 15

• 20