Question

You measure 22 textbooks' weights, and find they have a mean weight of 55 ounces. Assume the population standard deviation is 3.6 ounces. Based on this, construct a 95% confidence interval for the true population mean textbook weight.

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 30 bacteria reveals a sample mean of ¯x=78 hours with a standard deviation of s=6.2 hours. You would like to estimate the mean lifespan for this species of bacteria to within a margin of error of 0.8 hours at a 98% level of confidence.

What sample size should you gather to achieve a 0.8 hour margin of error? Round your answer up to the nearest whole number.

n =   bacteria

Answer 1