6.2 Confidence Intervals

Which z-value is used for a 95% confidence interval?

• 1.65
• 1.96
• 2.58
• 2.33

We plan to survey college seniors to see what proportion plan to attend grad school next year. Using 98% confidence, how many students should we survey if we wish the margin of error to be within 3%?

• approximately 1170

• approximately 1050

• approximately 1500

• approximately 40

What is the t value associated with 90% confidence and a sample size of 15?

• 1.341
• 1.345
• 1.761
• 1.753

Margin of Error is equal to:

• Standard Deviation

• 2 * Standard Deviation

• Critical Value

• Point Estimate

True or False: The more confident you want to be, the smaller your confidence interval will be.

• True

• False

Which of the following changes to a study would result in a smaller confidence interval?

• increasing the confidence level, increasing the sample size

• increasing the confidence level, decreasing the sample size

• decreasing the confidence level, decreasing the sample size

• decreasing the confidence level, increasing the sample size.

When the standard deviation is estimated from data, the result is called the ... of the statistic. 

• standard error
• confidence interval
• sample mean
• population mean

Which z-value is used for a 95% confidence interval?

• 2.58

• 1.66

• 1.96

• 2.33

Which of the following changes to a study would result in a narrower confidence interval?

• increasing the confidence level, increasing the sample size
• decreasing the confidence level, decreasing the sample size
• increasing the confidence level, decreasing the sample size
• decreasing the confidence level, increasing the sample size.

What is the degrees of freedom equal to?

• n
• n+1
• 1-n
• n-1