Confidence Intervals for Means Sigma Known

If the 95% Confidence Interval for a population mean is (114.56, 125.54), then is it likely that the true population mean µ is greater than 130?

• Yes

• No

• Not enough information

• I have no idea what you're asking of me

A 90% confidence interval for the mean speed driven by cars on Due West Road is given by (21, 45). What was the sample mean of this study?

• 12

• 24

• 33

• None of these.

A 90% confidence interval for the mean speed driven by cars on Due West Road is given by (21, 45). What was the margin of error of this interval?

• 12

• 24

• 33

• None of these.

A 90% confidence interval for the average salary of all CEOs in the electronics industry was constructed using the results of a random survey of 45 CEOs. The interval was $139,048 to $154,144. Give the interpretation of the interval.

• 90% of the sampled CEOs have salaries that fell in the interval $139,048 to $154,144

• We are 90% confident that the mean salary of all CEOs in the electronics industry falls in the interval $139,048 to $154,144.

• There is a 90% chance that CEOs in the electronics industry have salaries that fall between $139,048 to $154,144

• We are 90% confident that the mean salary of the sampled CEOs falls in the interval $139,048 to $154,144.

When we say we have a 90% confidence interval, what are we 90% confident of?

• That the population mean is within the interval boundaries

• That the population mean is outside the interval boundaries

• That the sample mean is within the interval boundaries

• That the sample mean is outside the interval boundaries

What are the critical z-values for a 80% confidence interval?

What are the critical z-values for a 90% confidence interval?

What are the critical z-values for a 95% confidence interval?

What are the critical z-values for a 99% confidence interval?

In a 90% confidence interval, what percent of the curve is in each tail?

• 5%

• 10%

• 45%

• 90%