Find the margin of error at a 80% confidence level for estimating the population mean if n=11,¯x=39 and s=6   Round your answer to 2 decimal places.

The confidence interval for a population mean is (7.43, 7.59). What are the sample mean and the margin of error? Margin of Error = Give your answers as decimals, to two places.

You are a researcher studying the lifespan of a certain species of bacteria.  A preliminary sample of 35 bacteria reveals a sample mean of ¯x=76x¯=76 hours. The population standard deviation is known to be 5.6  hours.  You would like to estimate the mean lifespan for this species of bacteria to within a margin of error of 0.4 hours at a 90% level of confidence. How many more bacteria should you sample to achieve a 0.4 hour margin of error? n =     bacteria

What percent of our campus is female? If no preliminary study is made to estimate, how large a sample is needed be 99% sure that the error will be no more than 0.03 from?

The distribution of scores on a standardized test is approximately Normal with standard deviation of σσ = 22. If a sample of 150 students had a mean score of x¯x¯ = 74.3, use this to find a 99% confidence interval for the mean score of all students on this test. We are 99% confident that the the mean score of students on this test was in the interval     What is the margin of error for your confidence interval? Margin of error =

The chart to the right shows that a professor's grading distribution is bell shaped, or normally shaped. The mean of the distribution is 74 and the standard deviation is 9. Using a Continuous Variable Normal Bell Distribution Model, calculate the minimum test score needed to score in the top 5% of the class. Complete your work in the worksheet by listing the formula inputs, labels for the formula inputs and make your calculations with formulas. This test problem is similar to what you studied in video # 32, 33 and 34 and homework problems # 17, 21 and 23. Relative Frequency Frequency Professor looks at all test score for a particular test (this is population data), and observes: 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 Mean = 74 Median = 74 Mode = 73 SD=9 0 0 0 up to 10 up 10 to 20 0 20 up to 30 0 30 up to 40 2 40 up to 50 29 50 up to 60 X = Score 112 60 up to 70 225 70 up to 80 111 80 up to 90 21 2 90 up 100 up to 100 to 110

State the null and alternative hypothesis if I claim that the mean lifespan of African elephants is 59 or less.

Estimate the true mean GPA of the freshman class with 99% confidence.