Using StatCrunch for Confidence Intervals

What is a point estimate?

• A single value used to estimate an unknown population parameter.

• A range of values used to estimate an unknown population parameter.

• A value that is not related to the unknown population parameter.

• A value that is only used in certain statistical models.

What does a confidence interval represent?

• A confidence interval represents the exact value of the population parameter.

• A confidence interval represents a range of values within which the true population parameter is likely to fall with a certain level of confidence.

• A confidence interval represents the average of the sample data.

• A confidence interval represents the upper bound of the population parameter.

Why is it important to interpret confidence intervals?

• To identify outliers

• To calculate the mean

• To understand the precision and reliability of the estimate.

• To determine the sample size

What StatCrunch command be used to compute confidence interval for a population proportion?

• Graph > QQ Plots

• Stat > Summary Stats > Columns

• Stat > Regression > Simple Linear

• Stat > Proportion Stats > One Sample > With Summary

What must be entered into StatCrunch to create a confidence interval for the population proportion?

• 1. 1. Value of x
     2. Value of n
     3. Confidence level

• 1. 1. Value of x-bar

  2. 2. Value of s

  3. 3. Confidence level

• 1. 1. Lower limit

  2. 2. Upper limit

  3. 3. Confidence level

• 1. 1. Shape

  2. 2. Center

  3. 3. Spread

What factors affect the width of a confidence interval?

• Sample size, level of confidence, and value of p-hat.

• Sample size, level of confidence, and standard deviation of the data.

• Sample size, level of confidence, and mean of the data.

• Sample size, level of significance, and median of the data.

A 95% confidence interval for the proportion of Cincinnati State students who smoke was found to be (0.10, 0.16). What is the correct interpretation of the interval?

• We are 95% confident that the population mean number of Cincinnati State students who smoke is between 0.10 and 0.16.

• We are 95% confident that the population proportion of Cincinnati State students who smoke is between 0.10 and 0.16.

• We are 95% confident that the sample proportion of Cincinnati State students who smoke is between 0.10 and 0.16.

• We are 95% confident that the population proportion of Cincinnati State students who do not smoke is between 0.10 and 0.16.

A 95% confidence interval for the proportion of Cincinnati State students who smoke was found to be (0.10, 0.16). What is point estimate of for the population proportion who smoke?

• p-hat = (0.16 * 0.10) / 2 = 0.008

• 95%

• p-hat = (0.16 - 0.10) / 2 = 0.03

• p-hat = (0.16 + 0.10) / 2 = 0.13

A 95% confidence interval for the proportion of Cincinnati State students who smoke was found to be (0.10, 0.16). What is margin of error for the interval?

• MOE = (0.16 * 0.10) / 2 = 0.008

• 95%

• MOE = (0.16 - 0.10) / 2 = 0.03

• MOE = (0.16 + 0.10) / 2 = 0.13

What are the three most common confidence levels for a confidence interval?

• 68%, 95%, and 99.7%

• 90%, 95%, and 99%

• 25%, 50%, 75%

• Depends on the value of the p-hat