Midterm 2 (Spring 2005)

# Midterm 2 (Spring 2005) - 7[15 Calculate the 99 confidence...

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Statistics Test 2 Prof. VanderHoff Spring 2005 All work must be shown on exam to receive credit. 1. [5] Calculate the probability that the standard normal variable [ z statistic] is between -.45 and 1.36. 2. [8] The mean of a standard test is 100 and the standard deviation is 13. What is the probability a test taker has a score greater than 135? 3. [8] The mileage obtained on a tire is normally distributed with a mean=50,000 and a standard deviation=3000. 2% of tires will exceed what mileage? 4. [8] The proportion of researchers who approve of a procedure is .6. What is the probability that 115 of a sample of 200 researchers would approve of the procedure? 5. [8] Suppose we have a random sample of 100. What is the probability of having a sample mean greater than 62.5 if the population mean=65 and the population standard deviation=12? 6. [10] Calculate the 99% confidence interval for the population mean using a sample of 64 with a mean=25 and a standard deviation=5.

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Unformatted text preview: 7. [15] Calculate the 99% confidence interval for the population mean using the following sample: x 4 9 1 6 2 1 8 1 8. [8] The proportion of students who travel during spring break is .4. What is the probability of less than 75 travels in a sample of 200 students? 9 [10] A sample of 81 students contains 33 who enroll in classes during the summer. Calculate the 99% confidence interval for the population of students who take classes during the summer. 11. [10] A sample of 120 students has an average time to commute of 28 minutes and a standard deviation of 4 minutes. Test the null hypothesis that the mean is less than or equal to 25 minutes. Use a 5% significance level. 12 [10] Test the null hypothesis that the population mean=300 [the alternative is the mean does not equal 300]. Use a 1% significance level. A sample of 25 has a mean=290 and a standard deviation=7....
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Midterm 2 (Spring 2005) - 7[15 Calculate the 99 confidence...

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