Confidence Intervals Mean T

An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.

What is the point estimate?

• 75

• 105.2

• 10

• 0.90

An IQ test was given to a simple random sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. It is desired to construct a 90% confidence interval for the mean IQ scores of the students at the college.

Find the Standard Error.

• 75

• 10

• 105.2

• 1.155

Which confidence would result in a wider interval (assuming nothing else changed), 91% or 97%?

• 97%, z* is larger for higher confidence intervals

• 97%, the standard error is larger for higher confidence intervals

• 91%, z* is larger for lower confidence intervals

• 91%, the standard error is smaller for lower confidence intervals

I have sampled 100 students and found that the 95% confidence interval for the mean is:

(7.5, 8.5)

• There is a 95% chance that the true mean falls between 7.5 and 8.5

• We are 95% confident that the true mean falls between 7.5 and 8.5

• There is a 95% probability that my true mean is between 7.5 and 8.5

• My margin of error is 95% of the data

What is the confidence interval being calculated in the image to the left?

• 90% confidence interval

• 95% confidence interval

• 99% confidence interval

• 35% confidence interval

We use confidence intervals to estimate

• parameters (population mean or population proportion)

• statistics (sample mean or same proportion)

• z-scores

• probability

Which is the correct program to use on the TI-84 calculator in order to calculate confidence intervals for population mean?

• STAT->

  TESTS->

  7:ZInterval

• STAT->

  TESTS->

  1:Z-Test

• STAT->

  TESTS->

  3:2-SampZTest

• STAT->

  TESTS->

  2:T-Test

It was found that in a sample of 90 teenage boys, 70% of them have received speeding tickets. What is the 95% confidence interval of the true proportion of teenage boys who have received speeding tickets?

• (0.61, 0.80)

• (0.591, 0.812)

• (0.584, 0.830)

• (0.65, 0.85)

In a survey of 104 students, it was found that 79 went to the homecoming game this year. Calculate a 99% confidence interval for p (true proportion of students that attended homecoming).

• (.59, .79)

• (.62, .85)

• (.60, .90)

• (.65, .87)

It was found that in a sample of 90 teenage boys, 70% of them have received speeding tickets.  What is the 90% confidence interval of the true proportion of teenage boys who have received speeding tickets? 

• (0.621, 0.780)

• (0.591, 0.812)

• (0.584, 0.830)

• (0.615, 0.805)