1. In a survey of 636 males ages 18-64, 390 say they have gone to the dentist in the past year. Construct 90% and 95% confidence intervals for the population portion. Interpret the results and compare the widths of confidence intervals.
2. In a survey of 6000 women, 3431 say they change their nail polish once a week. A 90% confidence interval for the population portion is (__,__) Round all intermediate values to the nearest thousandth.
3. A researcher wishes to estimate with 99% confidence, the proportion of adults who have high speed internet access. Her estimate must be accurate within 2% of the true portion.
What is the minimal sample size needed using a prior study that found that 54% of the respondents said they have high speed internet?
What is the minimal sample size needed assuming that no preliminary estimate is available?
4 . Country A 62%.. Country B 90%… Country C 93%
2585 adults from country A, 1112 adults from country B, and 1081 adults from country C were asked if human activity contributes to global warming.
Construct a 95% confidence interval for the adults from country A.
Construct a 95% confidence interval for the adults from country B.
Construct a 95% confidence interval from the adults from country C.
5. 400 adults from the east, south, midwest, and west were asked if traffic congestion is a serious problem.
East 36%,South 32%,Midwest 25%, West 53%
95% CI for the portion of adults from the west (__,__)
95% CI for the portion of adults from the East (__,__)
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