Statistics Confidence Interval

What is a confidence interval?

• A range of values that is likely to contain the true population parameter with no level of confidence

• A range of values that is unlikely to contain the true population parameter with a certain level of confidence

• A range of values that is likely to contain the true population parameter with a certain level of confidence based on a sample from the population.

• A range of values that is likely to contain the true population parameter with a certain level of confidence based on the entire population

What is the margin of error?

• The margin of error is a measure of the accuracy of a sample statistic.

• The margin of error is the difference between the highest and lowest values in a sample.

• The margin of error is a measure of the uncertainty or range of values around a sample statistic that is likely to contain the true population parameter.

• The margin of error is the average of the sample values.

Ho: mu = 145

CI = [140.7, 155.3]

• Reject Ho

  mu could be 145

• Fail to reject Ho

  mu is NOT 145

• Reject Ho

  mu is NOT 145

• Fail to reject Ho

  mu could be 145

mu of diff = 0

CI = [-1.3, 2.3]

• Reject Ho

  There is NOT a difference

• Fail to reject Ho

  There is NOT a difference

• Reject Ho

  There is a difference

• Fail to reject Ho

  There is a difference

A local bank needs information concerning the savings account balances of its customers. A random sample of 13 accounts was checked. The mean balance was $686.75 with a sample standard deviation of $256.20. Find a 95% confidence interval for the true mean.

• ($513.14, $860.36)

• ($525.59, $847.91) 

• ($533.27, $840.23)

• ($531.92, $841.58)

A sample of 20 cupcakes found the interval for calories to be (150, 350). Which is the correct interpretation of the 95% confidence interval?

• We are 95% confident that the true mean calorie content can be found with a sample of 150 to 350 cupcakes.

• We are 95% confident that the true mean calorie content in cupcakes is between 150 and 350 calories.

• We are 95% confident that a sample of 20 cupcakes will find 250 calories per cupcake.

• None of these are correct.

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

• 1.341

• 1.345

• 1.761

• 1.753

Which of the following does NOT have an affect on the width of a confidence interval?

• Sample mean

• t*

• Sample standard deviation

• Sample size

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

• 12

• 24

• 33

• None of these.

Find the t* value for a 99% confidence interval with a sample of 23 people.

• 1.714

• 1.711

• 2.064

• None of these.