Scope of Inference Statistics

If the boxes (IQR) overlap, it means the result found in the sample

• could be due to sampling variation

• is likely to be the case

• has too many errors

When looking at credits of Y12 boys and credits of Y12 girls at SSTS, if the ICI's overlap then you

• cannot make the call that the median credits of Y12 boys tend to be more compared to the credits of Y12 girls

• can make the call that the median credits of Y12 boys tend to be more compared to the credits of Y12 girls

A quality control inspector will measure the salt content (in milligrams) in a random sample of bags of potato chips from an hour of production. Which of the following would result in the smallest margin of error in estimating the mean salt content σ ?

• 90% confidence; n = 25 

• 90% confidence; n = 50 

• 95% confidence; n =25 

• 95% confidence; n =50 

• n=100 at any confidence level 

A random sample of 25 Ohio students had a mean ACT score of 21 with a standard deviation of 1.2.  Which of the following is the 95% confidence interval for the true average ACT score for Ohio students?

• (20.53, 21.47)

• (18.648, 23.352)

• (20.505, 21.495)

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.

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.

To test a claim about a mean, when the population standard deviation is unknown we use:

• z procedures

• Pythagorean Theorem

• t procedures

• np > 10 and n(1-p) > 10

What do we use to estimate unknown parameters?

• Hypothesis Test

• Confidence Interval

• Trig Identity

• Guess and check