Question

3)

You are a researcher studying the lifespan of a certain species of bacteria. A preliminary sample of 40 bacteria reveals a sample mean of ¯x=74x¯=74 hours with a standard deviation of s=7s=7 hours. You would like to estimate the mean lifespan for this species of bacteria to within a margin of error of 0.75 hours at a 90% level of confidence.

What sample size should you gather to achieve a 0.75 hour margin of error? Round your answer up to the nearest whole number.

n = ____ bacteria

4)

ou want to estimate the average weight in tons of loads carried by trucks through a particular stretch of road. From previous information the standard deviation is expected to be σ=16.1 tons. How many trucks must be weighed to estimate the the tons per truck to within 5 tons at a 98% level of confidence. Round your answer up to the largest whole number.

n = ____ trucks

5)
Assume that a sample is used to estimate a population mean μμ. Find the 80% confidence interval for a sample of size 47 with a mean of 73.8 and a standard deviation of 6.8. Enter your answer as an open-interval (i.e., parentheses) accurate to one decimal place (because the sample statistics are reported accurate to one decimal place).

80% C.I. =

Answer should be obtained without any preliminary rounding. However, the critical value may be rounded to 3 decimal places.

Answer 1