Confidence Intervals and Proportions

This video tutorial explains how to construct a confidence interval for a population proportion, using examples from election polls and other fields. It covers the necessary formulas and steps, including calculating the point estimate, error bound, and confidence interval. An example problem is provided to demonstrate the process of estimating the proportion of adults with cell phones in a city.

What is the confidence level typically used in election polls?

• 85%

• 99%

• 95%

• 90%

In the context of confidence intervals, what does the margin of error represent?

• The range within which the true population parameter lies

• The difference between the highest and lowest values

• The standard deviation of the sample

• The average of the sample data

Which of the following is NOT an example of a population proportion?

• Average income of a city

• Proportion of a population with a virus

• Percentage of stocks that increase weekly

• Proportion of households owning computers

What is the formula for the point estimate (p-prime) in a confidence interval for a proportion?

• x divided by n

• n minus x

• n divided by x

• x times n

In the formula for the error bound of a proportion, what does q-prime represent?

• The sample mean

• One minus p-prime

• The z-score

• The sample size

In the example problem, how many adults were surveyed to determine cell phone ownership?

• 421

• 500

• 250

• 1000

What is the calculated sample proportion (p-prime) for the cell phone ownership example?

• 0.421

• 0.500

• 0.158

• 0.842

What is the z-score used for a 95% confidence level in the example problem?

• 1.64

• 1.96

• 2.58

• 1.28

What is the error bound calculated for the cell phone ownership example?

• 0.032

• 0.042

• 0.052

• 0.022

What is the final confidence interval for the proportion of adults with cell phones in the example?

• 0.820 to 0.880

• 0.800 to 0.860

• 0.810 to 0.874

• 0.830 to 0.890