Interpreting and Constructing Confidence Interval

Which of the following is the correct way of interpreting a confidence interval?

• "We are C% confident that the interval from __ to __ doesn't capture the [parameter in context]."

• "We are C% sure that the interval from __ to __ captures the [parameter in context]."

• "We are C% certain that the interval from _ to _ captures the [parameter in context]."

How can we decrease margin of error?

Check all that apply

• The confidence level increases

• The confidence level decreases

• The sample size n increases

• The sample size n decreases

Which of the following conditions is false for constructing a confidence interval about a proportion?

• Random: the data come from a random sample from the population of interest

• 10%: when sampling without replacement, n<0.10N

• 10%: when sampling with replacement, n<0.10N

• Large Counts: Both np̂ and n(1-p̂) are at least 10

Which of the following conditions is false for confidence interval for a population mean?

• Random: the data come from a random sample from the population of itnerest

• 10%: when sampling without replacement, n<0.10N

What is the formula for one-sample t interval for population mean confidence interval?

A simple random sample of 50 driver education students showed the pictured number of hours driven at night prior to obtaining their driver's license. Construct a 90% confidence interval for the true mean number of hours students drive.

Choose the correct type of interval.

• 1 prop z interval

• z interval

• t interval

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, $154,144). Give a practical 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. 

• 90% of all 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.

A simple random sample of 160 travelers determined that the mean cost of a vacation in North America was $264 per day with a standard deviation of $68. Construct a 95% confidence interval for the mean vacation cost per day for all travelers.

Choose the correct type of confidence interval

• 1-Prop Z interval

• z interval

• t interval

A simple random sample of 730 registered voters shows that 65% of the registered voters favor raising taxes to pay for state parks. A 98% confidence interval for the true proportion of voters who will vote in favor or raising taxes is to be constructed. Which type of confidence interval should you choose?

• prop z interval

• z interval

• t interval

In a simple random sample of 482 lawyers, 136 had tried a case in court. A 80% confidence interval for the true proportion of voters who will vote in favor or raising taxes is to be constructed. Which type of confidence interval should you choose?

• z interval

• t interval

• 1 prop z interval