Ch. 10 Confidence Interval Review

Identify the confidence interval used in the figure below if each shaded area is equal to 0.05.

• 90%
• 95%
• 98%
• 99%

Tags

CCSS.HSS.IC.B.4

CCSS.HSS.IC.A.1

CCSS.HSS.ID.A.4

The confidence level of an interval estimate of a parameter is the probability that the interval estimate will contain the parameter.

• True
• False

Tags

CCSS.HSS.IC.B.4

CCSS.HSS.IC.A.1

CCSS.HSS.ID.A.4

A research company wants to estimate the proportion of people who like oatmeal.  They want the confidence level to be 95%.  The company gets 325 people to sign up for the survey, but on the day that the survey is issued, only 250 people show up and take the survey.  What happens to the confidence interval?

• It gets larger
• It gets smaller
• It stays the same
• Too little information given

Tags

CCSS.HSS.IC.B.4

CCSS.HSS.IC.A.1

A sample of 400 racing cars showed that 80 cars cost over $700,000. What is the 99% confidence interval of the true proportion of cars costing over $700,000?

• 0.001 < p < 0.005
• 0.566 < p < 0.693
• 0.148 < p < 0.252
• 0.023 < p < 0.045

Tags

CCSS.HSS.IC.B.4

CCSS.HSS.IC.A.1

CCSS.HSS.ID.A.4

A recent study of 750 Internet users in Europe found that 35% of Internet users were women.  What is the 95% confidence interval of the true proportion of women in Europe who use the Internet? 

• 0.321 < p < 0.379
• 0.316 < p < 0.384
• 0.309 < p < 0.391
• 0.305 < p < 0.395

A study found that in a sample of 44 subjects, 9 of agree that children under 6 shouldn’t be taken to nice restaurants. Calculate a 95% confidence interval for p.

• (0.105, 0.305)

• (0.082, 0.318)

• (0.117, 0.292)

• (0.048, 0.361)

Tags

CCSS.HSS.IC.B.4

A study found that in a sample of 44 subjects, 9 of agree that children under 6 shouldn’t be taken to nice restaurants.

The 95% confidence interval for p is (0.082, 0.318). Interpret this interval.

• 95% of the time the proportion of people who believe children under 6 shouldn't be taken to nice restaurants will be between 8.2% and 31.8%.

• The population proportion of people who believe children under 6 shouldn't be taken to nice restaurants is between 8.2% and 31.8%.

• The probability that the proportion of people who believe children under 6 shouldn't be taken to nice restaurants will be between 8.2% and 31.8% is 95%.

• Based on this sample, I am 95% confident that the proportion of people who believe children under 6 shouldn't be taken to nice restaurants is between 8.2% and 31.8%.

Tags

CCSS.HSS.IC.B.4

CCSS.HSS.IC.A.1

A preliminary study suggests that 17% of people agree on an issue. How large must your sample size be so you could be within ± 5% with 95% confidence?

• 217

• 30

• 2

• 152

Tags

CCSS.HSS.IC.B.4

CCSS.HSS.IC.A.1

Find the critical value, z*, for 91% confidence.

• 1.70

• 1.34

• 0.18

• -1.34

Tags

CCSS.HSS.ID.A.4

Which confidence would result in a wider interval (assuming nothing else changed), 91% or 97%?

• 97%, z* is larger for higher confidence intervals

• 97%, the standard error is larger for higher confidence intervals

• 91%, z* is larger for lower confidence intervals

• 91%, the standard error is smaller for lower confidence intervals

Tags

CCSS.HSS.ID.A.4