- If The Sample Size N Is Doubled By How Much Is The Length Of The Confidence Interval On U In A 99 Confidence Interval 1 (61.95 KiB) Viewed 49 times
If the sample size n is doubled, by how much is the length of the confidence interval on u in a 99% confidence interval reduced? What happens to the length of the interval if the sample size is increased by a factor of four? Ishikawa et al. (Journal of Bioscience and Bioengineering, 2012) studied the adhesion of various biofilms to solid surfaces for possible use in environmental technologies. Adhesion assay is conducted by measuring absorbance at A590. Suppose that for the bacterial strain Acinentobacter, five measurements gave readings of 2.69, 5.76, 2.67, 1.62, and 4.12 dyne-cm². Assume that the standard deviation is known to be 0.66 dyne-cm². (a) Find a 95% confidence interval for the mean adhesion. (b) If the scientists want the confidence interval to be no wider than 0.55 dyne- cm². How many observations should they take?